The developer kicked off a project to regenerate Watford's Charter Place shopping centre was paid more than £500,000 in compensation, the Watford Observer has learned.

Henry Boot Ltd received around £540,000, a large portion of which was shouldered by the taxpayer, after Watford Borough Council switched the project to the owners of the Harlequin.

The leaked figure can be revealed after Watford Borough Council kept it secret from the taxpayer, citing confidentiality reasons.

This week the council was attacked by opposition politicians for keeping Watford taxpayers in the dark over how their money was being spent.

Steve Rackett , the leader of the Green Party, said: "It is not good when the council cannot be open with the public about taxpayers’ money.

"It looks like the council is becoming increasingly secretive about how it spending large amounts of taxpayers’s money."

However, Watford’s Liberal Democrat mayor, Dorothy Thornhill, defended the council’s decision not to reveal the figure paid to Henry Boot, saying there had been a confidentiality agreement.

She said if the council had revealed the amount itself it could be sued by Henry Boot, which would cost the taxpayer more money.

Mayor Thornhill said: "All I will say to the Greens is if they held the mayoralty they would understand there are some things that you just can’t do.

"We are the open party, we have done more to open up town hall than Labour did in 30 years. My party is instinctively open.

"But when my solicitor tells me we can’t do this I take the advice. The last thing I want is the council in court."

The Charter Place figure has been leaked after bosses at the council blocked attempts by the Watford Observer to obtain it from the borough’s accounts.

This week council bosses denied a request for access to the agreement and invoices between Watford and Henry Boot, claiming they are commercially confidential.

The Watford Observer also tried to exercise a citizens’ rights, under the Audit Commission Act 1998, to inspect other contracts the council has with companies to see how public money is being spent.

However, council bosses redacted crucial parts of the contracts, again claiming commercial confidentiality, leaving the Watford taxpayer in the dark of how much deals negotiated on their behalf are costing.

The revelation of the Charter Place payoff figure has prompted calls for swift progress to be made over the project, which has been beset by problems and delays.

The council decided to end its agreement with Henry Boot in June and handed it to Capital Shopping Centres, owners of the Harlequin, after it expressed interest in the project. The scheme aims to totally redevelop the tatty shopping precinct with a new building and plans for a cinema.

Steve Johnson, a Conservative borough councillor, said: "They have got to get building the thing - at the end of the day that is the important thing.

"We need to see it realised. All we are doing at the moment is outlaying money with nothing happening there."

Mayor Thornhill said the deal negotiated with Capital was a much better deal for the taxpayer than the Henry Boot one and would recoup the money lost in the payoff within the first year.