The Government paid at least 30 consultants up to £2,000 a day last year, an investigation has revealed.
According to figures obtained by the BBC Newsnight programme, the specialists were hired by six different departments.
Ten were taken on by the Department of Transport, eight worked at the Ministry of Justice, five at the Department of Energy and Climate Change, four at the Home Office, two at the Treasury and one at the Ministry of Defence.
The Government told the BBC it paid £317 million to consultants in 2013, but insisted overall spending on them had dropped by three quarters since 2009.
In addition, separate figures show the MoD spent £137 million on technical consultants over the same period above and beyond that total, Newsnight said. It also told the programme it had recently employed someone earning up to £3,000 a day.
The figures, obtained via a Freedom of Information request, prompted a backlash from campaigners and unions who questioned the high fees and urged ministers to set out in detail how many people were being hired and for how long.
Jonathan Isaby, chief executive of the Taxpayers’ Alliance, said: “I think people will be extremely concerned about the number of consultants being paid vast amounts of money for a day’s work in government.
“Government is rightly reducing the headcount of the civil service but you cannot negate that by paying huge amounts to consultants instead.
“I think there are big questions about whether we are getting value for money not least because there is a severe lack of transparency about what they are actually doing.”
Leslie Manasseh, deputy general secretary of Prospect, the union which represents professionals across the civil service, said there was confusion about how the Government did its sums.
He said cuts in Whitehall had led to departments hiring a “growing” number of consultants and managers.
“This is taxpayers’ money and they have a right to know how it is being spent,” he went on.
“We know how much the Prime Minister earns, we know how much senior civil servants and other politicians earn, we have little or no idea how much individual consultants are earning.”
The Government would not give Newsnight details about the number of consultants earning more than £1,000 a day, but it said it had brought this kind of spending under control.
A spokesman said: “This Government has scrutinised spend by departments like never before. Already it has put an end to excessive spending on consultants and interim staff by establishing stringent controls.
“Certain departments do however have a requirement for specialist roles, especially where they are undertaking complex transformative projects. Such roles are only authorised where the skills are not readily available within the civil service.”