Scores of ministers and officials are cashing in on their time in office by picking up lucrative jobs in the private sector.

Many are working in the very sectors they used to regulate while in government. Those taking advantage of this 'revolving door' include Danny Alexander, the Lib Dem former Treasury chief.

After losing his seat at last year's election he has been taken on by a Chinese-run bank. Whitehall watchdogs have stipulated only that he must not exploit the 'privileged information' he picked up as George Osborne's deputy.

Sir Danny can still lobby his former colleagues, allowing him to try to cash in on his Treasury contacts.

Despite rules against the use of insider information, hundreds of former public servants are pocketing jackpot wages from private firms.

In-depth analysis by the Daily Mail shows that the stampede has barely slowed despite a promise of action from David Cameron in 2010.

On leaving a government department two-thirds of ministers and officials now take a private job in the same sector.

Acoba, the appointments watchdog, has dealt with 371 individuals since 2008 and 247 of them followed this route. Not one application for clearance was turned down.

Jobs waved through include:

Roles in the energy sector for six former energy ministers;

Charles Hendry signed up for Britain to get electricity from Iceland then took a job with a firm working on the project;

Ed Davey struck a money-spinning nuclear deal with EDF and now works for a lobbying firm that has the French firm as a client;

Fourteen out of 15 trade and business ministers went into the City or commerce and six out of nine health ministers took jobs with health firms;

A diplomat who 'helped halt' a corruption inquiry into the Saudis and BAE Systems later took directorship with the defence firm;

Sir Henry Bellingham used his position as Africa minister to lobby Mozambique in support of a mining company he now chairs, on £4,000 a month.

Taking advantage: Former Lib Dem Treasury chief Sir Danny Alexander works for a bank

Before taking up roles outside government, ministers and senior civil servants have to apply to Acoba – the Advisory Committee on Business Appointments – which examines any potential conflicts of interest.

Appointed under the auspices of the Cabinet Office, its job is to scrutinise job applications and stop outgoing ministers and mandarins exploiting their 'insider information'.

It can advise the Prime Minister that a particular minister or crown servant's job application is 'unsuitable' – but it has never wielded this power.

Instead it issues 'advice' such as: 'For two years from his last day in ministerial office, he should not become personally involved in lobbying the UK Government.'

The civil service – once a job for life – is now increasingly seen as a taxpayer-funded springboard to personal riches in the private sector.

In the Treasury, 17 out of the 21 civil servants who applied for clearance left public service for jobs in the banking or business worlds.

Of 41 from the Ministry of Defence, 32 were poached by arms firms or other defence-related companies, the Mail's dossier shows.

Bernard Jenkin, who chairs the Commons public affairs committee, demanded a complete revamp, saying: 'Acoba is an advisory body, with no regulatory powers and is frequently ignored.'

David Davis, Tory MP and former chairman of the public accounts committee, said it should be mandatory for senior public servants to take two years of purdah.

'There should be a clear break, whether that's former ministers, senior civil servants or generals,' he said. 'Acoba is far too weak. It has given lots and lots of exemptions. It almost seems like exemptions are the norm.

'Cabinet ministers and senior civil servants are not underpaid. It shouldn't be that they just go off and take work where they use their influence and their contact network.

'It simply compounds the problem if a British government minister goes and works for any foreign power.' Alistair Graham, former chairman of the Committee on Standards in Public Life, said: 'The problem is we don't know what goes on behind closed doors.

Springboard: On leaving a government department two-thirds of ministers and officials now take a private job in the same sector. Pictured, MPs in the House of Commons

'It is very difficult to control these things. It may well be that people are abusing their past experience of government for personal advantage.'

Paul Flynn, a Labour MP and member of the Commons public administration committee, said he had no idea the situation was so bad.

'It's a deep-seated and growing scandal, where MPs are allowed to prostitute their insider knowledge to the highest bidder,' he added.

'These people are appointed for their contacts, the people they know, to oil the wheels. They should be banned.'

He said Acoba was less watchdog, more 'pussycat without teeth and claws'.

Last month Baroness Browning, who chairs Acoba, told MPs her committee was worried about the trend toward ministers seeking employment in the sectors they had responsibility for.

She said the watchdog had neither 'the resources nor the remit' to make the significant changes required.

The former Tory minister called for the power to take ministers to court if they took jobs against Acoba's advice.

Douglas Carswell, the Ukip MP for Clacton, said: 'Some of these people are trading on insider information – in any normal marketplace, they'd expect to join Bernie Madoff in prison, but in politics it seems to be a way of life.