If you ever meet John Lees at a party, make sure you have filled your glass before you ask him what he does for a living. He might talk about being a career coach, mention that he writes books on business, tell you about his recent keynote speech at a conference in Olympia, or drop in the fact that he's also a part-time Anglican priest, based in Cheshire.

"I've got a classic portfolio career," says Lees, 50. "The advantage is that by working for a variety of employers and organisations, no one has complete power over you to switch work on or off. The drawback is that I have an immensely complicated diary."

Property Portfolio Rescue, which specialises in selling property for those in financial distress, says that inquiries have almost doubled since last year. The fastest-growing sector is homes worth £500,000 (Dh2.72 million) or more, which are selling at knock-down prices, indicating a dramatic change in fortunes among those for whom job security used to be a given.

To counter this, growing numbers of professionals are reinventing themselves by setting up as portfolio workers in a new employment phenomenon dubbed Giganomics. Here, instead of jobs for life, we rely on a series of "gigs," some regular, some not.

Former Vanity Fair and New Yorker editor Tina Brown, who coined the term, writes on her influential Daily Beast blog: "No one I know has a job anymore. They've got gigs: A bunch of free-floating projects, consultancies and bits and pieces they try to stitch together."

Brown notes that the white-collar casualties of the downturn have become serial networkers, touting for business at every opportunity. "What's new is the way the Gig economy has hit the demographic that used to assume a college degree from an elite school was the passport to job security."

Brown paints a bleak picture of freelancers' lives, likening them to hustlers, burdened with all the "anxieties, uncertainties and indignities of Gig Work," grafting three times as hard for the same money as a salaried employee, without any of the benefits, such as sick and holiday pay or a pension.

Nick, 37, a graphic designer based in London, can attest to the stress felt by workers who have no desire, or indeed flair, for the hand-to-mouth existence of portfolio working.

"I was made redundant two years ago and went freelance," he says. "I hated it, because I am terrible at selling myself, and I'm not laid back enough to live with the insecurity of not knowing where I'll be in six months. I managed OK, and I earned as much as I had done previously, but there was a price to pay in terms of sleepless nights."

Ironically, in the current climate of downsizing, playing the Giganomics game can leave workers feeling more, not less, secure; if one gig gets cancelled, you can rest easy knowing you have a handful more on the go.

Suzy Walton, a former senior civil servant and mother of four, with a background in central government, including the Ministry of Defence and the Cabinet Office, has taken up a series of non-executive directorships. A portfolio career has proved a lucrative - and immensely satisfying - alternative to corporate life. Walton, 45, boasts a resumé that makes Nicola Horlick look like a slacker.

"I sit on the boards of a military organisation Combat Stress, which looks after veterans with post-traumatic stress disorder, the Internet Watch Foundation, which is the body that regulates the Internet and Birmingham Children's Hospital," she says. "Then there's the board of the University of Westminster, the Government's science advisory council, an NHS group with a budget of £3 billion and a few others."

Walton, a chartered director, admits that none of these roles generates a substantive salary on its own - a standard NHS Trust would pay £7,000-£8,000 a year to a non-executive board member for a couple of days a month, and a FTSE 250 company might pay about £30,000 - but when combined, her directorships provide a good income. Just as importantly, she enjoys the challenges of spreading herself across so many fields.

"It puts pressure on me, being in so many sectors, and it's hard to keep up to speed with the issues in each, but I enjoy that. A portfolio career isn't for the fainthearted; there's a zero-tolerance attitude to being late or missing a commitment because of a medical appointment. But it's a fantastic lifestyle."

Anyone intending a pick-and-mix approach to work needs to be excellent at time management. A thick skin is also very handy, as freelancers who work from home are prone to paranoia when their e-mails go unanswered or their calls unreturned for days.

The upside is the freedom to pick and choose work, and to do it at a time that suits. Cary Cooper, professor of organisational psychology and health at Lancaster University, says it's a classic swings and roundabouts scenario.

"The good news is that you're supposed to have control over what work you do. The bad news is that you feel you can't say 'no' to anything," he says. "You should also be able to have a better work-life balance. But the people who employ you expect you to be on call whenever they want you."

The creative industries such as advertising, graphic design, and the media already rely heavily on freelancers, as does IT. The current slew of job losses means that many more companies will need portfolio workers in future.

"There's going to be much more multiple part-time working," says Professor Cooper. "Organisations are getting rid of staff, but they will buy back some of them on a portfolio basis because they can't do without them."

A recent report by Friends Provident into the changing face of the British workforce revealed that where once the average worker might have had a handful of jobs centring round the same career, some 13 million of us plan to change our occupation at least twice in our working lives. On average, each worker has had four jobs and a fifth plan to change jobs at least four times in the next 25 years. While 24 per cent said they would make a career change for a higher salary, 27 per cent were motivated by the prospect of job satisfaction.

"We found that UK workers want to develop their skills through new careers," says Martin Palmer, head of corporate pensions marketing at Friends Provident. "It's a shift from the traditional concept of a 'job for life'-style career to a more modern, fluid approach to working."

Southampton-based married couple Keegan Wilson, 35, and Claire Adam, 33, run three businesses: Public relations company Substance PR, a literary magazine called Pop Cult, and Genie, a glass-recycling collection service.

"The PR company is our bread and butter, and funds the other ventures," says Wilson. "The magazine I feel passionate about, but I have no high expectations that it will make a huge amount of money. The glass-recycling business is more of a risk, because we have no experience in that field, but we can afford to try it because we're not investing all our eggs in one basket. We get out and physically collect the glass, and that sort of manual labour can be enormously therapeutic."

A gift for combining roles is, without doubt, at the core of Giganomics, which is why women, with their innate ability to multi-task, are particularly unfazed by the prospect of taking on a raft of responsibilities.

Antonia Chitty trained as an optometrist and practised for five years, but now writes books on parenting and business, runs a PR company specialising in baby and child goods and services, and does research and policy work for health organisations, including the visual impairment charity SeeAbility and the College of Optometrists. She also has three children, Daisy, six, three-year-old Jay and a newborn baby boy, Kit.

"When you have children, you want to go home and see them," says Chitty. "I decided to work for myself because the alternative just wasn't viable, and this is the only way I can see school plays without colleagues frowning at me for having yet another afternoon off.

"I don't have a boss, I have a number of clients, and I plan my days in a way that suits me. Having worked this way I can't imagine ever going back to an office again - it would be far too restrictive."