Contractor Active Construction had been on site just six weeks in Holbrooks Park when vandals launched their first attack.

They torched a tractor being used to upgrade drainage on the football pitches which are being improved alongside construction of a new £500,000 pavillion.

Active signed up a security firm to protect the site.

But the arsonists returned the next night and set fire to the firm’s three remaining machines.

The yobs came back again the following day and were chased off by a security guard before returning with a pitbull dog to threaten him.

Paul Roberts, construction director at Active Construction, told the Coventry Telegraph: “What’s happened with the equipment will delay the drainage work.

“It’s a threat to the whole project. I’m sure the council are asking themselves is it worth it – do they push ahead and deliver it?

“Hopefully they will want to carry on because this is a terrific project.”

Site manager Chris Amos said: “It’s the minority ruining it for the majority. There’s real interest in the scheme – we’ve had lots of people coming up to us and asking us what’s going on.

“We’re part of the considerate contractors scheme so there are signs up telling people what’s going on.

“Unfortunately several have either been stolen of vandalised.”

Roberts added: “In all my working years I’ve never had a problem like this.

“We’ve had the odd thing stolen but no trouble on this scale.”

A spokesman for Coventry City Council told the Coventry Telegraph it was too early to say if the setback would lead to the project being delayed.

He added: “This project will greatly improve the facilities in the park for local people.

“Unfortunately since work began there have been some instances of anti-social behaviour and we are talking with the contractors to look at the options for increasing security.”