Executives at a company brought in to manage the decommissioning of the Sellafield nuclear plant have been forced to repay thousands of pounds in expenses after an audit uncovered extravagant claims, including a £714 taxi bill to "repatriate" a senior manager's cat.

The revelations emerged a day after the same managers were found to have paid themselves more than £6m in bonuses over three years, despite a string of failings at the Cumbria plant.

Bosses at the publicly funded Nuclear Management Partners also used expenses claims met by the taxpayer to pay for travel junkets to the US Masters golf tournament and gourmet dinners in France, according to the government spending watchdog.

The company was awarded a contract to run the plant for up to a maximum of 17 years from 2009, with a break clause after five years.

A National Audit Office report found that costs spiralled from £47bn, when NMP began work on the site in 2009, to £67bn by 2012 after key deadlines were missed.

In June, the company was fined £700,000 and ordered to pay more than £72,000 in costs after it sent bags of radioactive waste to a landfill site in Cumbria.

The audit of 606 documents covering the period 2008-12 found claims of £236,781 were requested without proper description, while £30,557 was spent purely on personal items. £42,711 should not have been claimed at all.

One executive claimed £714 for a taxi for themselves "and the cat", while another claimed £719 for Amazon purchases without receipts and an £82-per-head gourmet dinner in France.

Other claims included £2,795 on flights to the US Masters golf tournament in Augusta, Georgia, and a £2,316 Apple desktop computer.

Beggars belief

Jamie Reed, Labour MP for Copeland in Cumbria, in which Sellafield is located, said: "A workforce that is being asked to accept many changes - including pay restraint - will have many questions.

"Taxis for cats and flights to the US Masters simply beggars belief."

In answer to a parliamentary question from former SDLP leader Margaret Ritchie, energy minister Michael Fallon revealed that a total of £6.6m was paid out in bonuses.

Ritchie said: "The government and the NDA have serious questions to answer about this. It is unacceptable for this amount of public money to be paid in bonuses to a private consortium whose management of the decommissioning process at Sellafield has been so appalling.

"This is a consortium who in 2010/11 failed to meet targets in 12 of 14 major projects, yet in the same year senior executives received over £2m in bonuses."

NMP executives received £1,999,192 in bonuses in the financial year 2009/10. In 2010/11 the figure was £2,451,269, and in 2011/12 the pot totalled £2,148,035.

The taxpayer-funded bonuses for senior staff were paid for using funds from the Nuclear Decommissioning Authority, the non-departmental public body which agreed the terms of Sellafield's operating contract.

The bonuses are likely to come under close scrutiny after a series of setbacks at the site, which according NMP deputy managing director George Beveridge described as the most hazardous industrial building in western Europe.

NMP, which is owned by the UK's Amec, France's Areva and US company URS, admitted that some claims had been "incorrectly registered" but said there was no suggestion of impropriety.

The company has reimbursed all inaccurate claims, it said. However, it defended its bonus scheme.

"There is a clear link between the payment of bonuses and performance," said a spokesman. "2012/13 bonus levels - not included in the data quoted - were lower to reflect this year's performance in that financial year."

The NDA is reviewing NMP's performance to decide on whether to enact the break clause.