David Cameron has spent more than £680,000 of public money renovating Downing Street in the year that his government inflicted the biggest ever spending cuts across the public sector.

Records of all government spending reveal nine bills for the refurbishment of Downing Street including £30,000 for work he and his wife, Samantha, carried out on the No 11 flat last summer. The centrepiece of their revamp was the kitchen.

No 10 has confirmed that the full £30,000 grant for upkeep of the living accommodation, which is available to prime ministers annually, was used for the refit of 11 Downing Street, after the Guardian discovered the payment in the official spending records.

A spokeswoman said the money was spent on rewiring, plumbing and decorating but insisted the Camerons paid for the extras. "No public money was spent on furniture, fittings or accessories," she said.

The other £653,192.34 was spent on external and internal renovation of the offices and reception rooms in Downing Street, including cabling, plumbing and energy efficiency improvements. No 10 declined to specify further what the money was spent on and has previously refused Freedom of Information requests asking what changes have been made to the Grade I listed building since the election and the costs.

A spokesman said: "This spend relates to the Downing Street Building Modernisation Programme launched in 2006, under the last government, to address structural repairs and the renewal of failing infrastructure, having gone without refurbishment for some 50 years. This work is still ongoing. Downing Street is a Grade I listed building. As such it requires a certain level of maintenance. The prime minister has paid for changes to the flat out of his own pocket, beyond the annual maintenance budget threshold."

Tom Watson, the Labour MP for West Bromwich East, who has been campaigning for greater openness about the financing of Downing Street, described the £30,000 grant as a "hidden bonus for the PM" to supplement a flat he lives in rent-free.

He said: "£30,000 is more than a nurse's salary. People need to know what's gone in there and how much it's cost. It's not their building, it's the nation's building.

"The PM heralded the age of transparency and said we're in a for a period of austerity. Lo and behold the taxpayers subsidised a £30,000 kitchen and he's refusing to give all the details. He's not living up to his pledges.

"He has to come clean about his own taxpayer's subsidy. He's supposed to be setting an example to rest of public sector."

The Cabinet Office's database of all items of spending above £25,000 (pdf), updated this week to the end of March, reveals that since the election the exchequer has funded a £683,102.34 refurbishment of Downing Street in total. There could be even more payments below that threshold.

The nine separate payments were made to Ecovert FM, the company that manages all Cabinet Office buildings, since November.

The Camerons occupy the four-bedroom flat above 11 Downing Street, as the Blairs did before them, because it is bigger than the one above No 10. The kitchen is in addition to a second catering kitchen in the property and a planning application for structural work lodged with Westminster council last year to move a doorway and build a wall. The work is particularly costly because of the historic nature of the building. English Heritage are involved in decisions about nearly all modifications.

Contracts for the renovations were only accessible because the coalition has begun to routinely publish details of all spending over £25,000. Watson said pledges of transparency were undermined by the government's refusal to give any detail on the payments.

Downing Street has separately refused an FOI request from Watson for fuller details of the refurbishment costs. The Information Commissioner's Office, which is responsible for enforcing the Freedom of Information Act, has since issued a demand for records held by the Cabinet Office about the nature and the cost of the work.

A spokesman for the ICO declined to comment because the situation was current.