A rebel party has racked up debts of nearly £29,000 on public funds with rivals warning: “It will be the taxpayer that will have to pay for this.”

An investigation by the Observer can reveal the Independent Labour group (ILG) which broke away from Labour last May, overspent Harrow Council money on staff members during its brief administration, while both Labour and the ruling Conservatives have underspent.

Each party is allocated a pro-rata sum of money to spend on running its office at Harrow Civic Centre that reflects the number of councillors its has. However, the cost of the eight-strong Independent Labour group hiring ‘a political assistant and two temporary administrative assistants’ while in power was actually more than its allotment.

The two major parties – both with 25 councillors each and therefore a larger allotment of council money – employ the same level of staff or less.

A Freedom of Information Act response revealed Labour is £35,961 in credit, the Conservatives are £10,019 in the black while the Independent Labour Group is £28,969 in the red.

David Perry, leader of the Labour group, said: “It will be the taxpayer that will have to pay for this overspend and, to make matters worse, the Tory administration are not clamping down on this as a result of the backroom deal they made with the Independent group in return for its support for the Conservatives taking control.”

Independent Labour said in a statement: “We have saved taxpayers a lot more than £28,000. In fact, the savings were around £32,000 since our administration made savings during its five months’ tenure by not having 10 cabinet members, unlike the Conservatives or Labour.

“Our leader, Thaya Idaikkadar, held three portfolios, while other portfolio holders also worked doubly hard by performing jobs for multiple cabinet positions without extra allowances for the additional positions, resulting in excellent value for money for taxpayers.

“The answer to all these issues is to overhaul and review the system in order to put the needs of our residents first.”

Labour councillor Bill Phillips queried ILG’s office budget at a cabinet committee meeting last month. Councillor Paul Osborn (Conservative), cabinet member for communications, performance and resources, said in response group offices come under a large departmental budget that is forecasting an underspend of nearly £500,000 this year.

Mr Osborn said: “Due to group offices using fixed term contracts for staff, the most prudent and often most cost-effective time to reorganise group support is after an election cycle.

“This will happen post-May, as it always does.

"The accusation of a deal is unfounded nonsense, and I'm amazed Labour are giving lectures on public spending given they spent £13,000 of taxpayers money on a glass wall for their leader's office.

"Of course the merits of their leader having a better view of the staff are undermined if, a few years later, said staff defect with the new leader when he forms his own group."