The Charity Commission spent more than three times its budget on agency staff in the past financial year, figures from the regulator show.
At an open board meeting in London yesterday, trustees heard that the commission's performance, measured by a range of key performance indicators, had continued to improve despite a 20 per cent fall in staff numbers since 2005.
But the figures show that the regulator spent £540,000 on temporary staff in 2009/10 against a budget of £160,000 – an overspend of 238 per cent.
The overspend was due to a "higher than anticipated use of agency staff to cover peaks in workload and to provide interim cover for business-critical, specialist roles", according to board papers presented at the meeting.
The papers say the budget has historically been exceeded and a "more realistic" amount had been set for 2010/11.
The regulator spent £310,000 less than its budget on postage and printing, and £250,000 less than its budget on accommodation.
Sarah Atkinson, head of corporate affairs at the commission, also noted a decline in the number of MPs who were trustees of charities after the general election.
She said the regulator's figures showed that, of the 232 MPs elected for the first time, only 32 were trustees. This resulted in a net loss of 40 trustees compared with the last parliament, she said.
Dame Suzi Leather, chair of the commission, said the drop was "quite noticeable at a time when there is such a great emphasis on the charity sector".
She said she hoped the All-Party Parliamentary Group on the Community and Voluntary Sector would encourage more MPs to become trustees. "Being a trustee gives an insight into the effect of public expenditure cuts on charities," she said.