Garda unions and opposition deputies have criticised the Department of Justice for failing to replace patrol cars which are forced off the road because of their high mileage.

Up to 150 garda cars were ordered off the road by senior officers upon clocking up 3oo,oookm in the first nine months of the year. this is double last year's scrappage ratio according to figures from the Garda Commissioner's office.

However, Alan Shatter, the Justice minister, told Finian McGrath, an independent TD for Dublin North Central, last month that while 144 vehicles had been taken off the road for high mileage, most of them had been replaced. The size of the garda fleet had fallen from 2,740 on December 31, 2O1O to 2,703 on September 15, according to Shatter.

Gardai and TDs now say that replacements have stopped due to funding constraints. They say that Donegal, Cavan-Monaghan, Kerry and Sligo are among the divisions where serious gaps in patrol-car coverage have emerged. The Association of Garda Sergeants and Inspectors (AGSI) claims there has been no funding for patrol-car replacement since early 2011.

The Garda Representative Association (GRA) warned that the service gardai provide to the public is diminished when basic tools - including vehicles - are not available.

Damien McCarthy, the GRA president, said: "Our members have reported many patrol cars being withdrawn and not replaced.  "Funding is a political decision. The political elite are asking the Garda Commissioner to police this country without the appropriate resources. Garda numbers are being reduced at the same time as budgets are constrained."

John Redmond, the deputy general secretary of AGSI, said many garda units were being told to "nurse" cars nearing the 300,000km mark by using them only for essential work.

"If they have to go to court in Dublin, they can't take the patrol car, even though they are only supposed to take official transport," he said.

"The other option is to use public transport, but if you have to bring a hatchet to court [as evidence], you can't be lugging that on the bus in your uniform."

Robert Troy, a Fianna Fail TD for Longford Westmeath, said that Mullingar town had lost one car to high mileage, and officers were now using a van to deliver summonses to homes in some estates, while nearby Edgeworthstown had lost its patrol car and was being covered from Granard.

"Criminal gangs wouldn't have to have Einstein in their midst to work out what district station was down a patrol car, or where was the weak link in the chain," Troy said. "The post office was robbed in Edgeworthstown just a few weeks ago."

The Department of Justice said allocation of resources was a matter for the Commissioner as the accounting officer of the force.