The agency is in a dispute with around 80 farmers in north Meath over the value of land which has been the subject of compulsory purchase orders (CPOs).

It has been forced to serve possession orders on the owners so it can build the motorway without securing ownership of the land.

The move is likely to increase the cost of the project as the NRA will now have to pay interest on the compensation due to the landowners for the period between it taking possession of the land and it finally purchasing it.

Seamus McGee, chairman of the M3 Landowners Group, which is representing the farmers, said that the dispute was due to the NRA's "penny pinching".

He claimed that the NRA was consistently offering farmers just one-third of the market value of their land. "We hire our own independent valuers and get one price and then they bring in their own guys and put it at a different price, " said McGee.

He said that the farmers weren't opposed to the CPOs but wanted realistic offers from the NRA for their land.

McGee said it was particularly frustrating as the farmers had been involved in the CPO process for several years but that "once they give you a notice to treat [an invitation to start price negotiations], the value is written in stone".

However, a spokesman for the NRA said that it had no policy of deliberately undervaluing the land involved in its CPOs. "We don't seek to influence the prices set by our independent valuers and we don't have the legal power to alter their findings, " he said.

"If anything, we're trying to speed up the CPO process for our projects because it's in the landowners' interest to do so."

He said that the NRA was increasingly referring cases to property arbitrators for binding decisions. This process, however, can be quite slow as there are only two arbitrators in the state.

According to John Morley, a consultant with Savills Hamilton Osbourne King's professional services team, the problems experienced by the NRA stem from the confrontational nature of the current CPO system.

"People tend to adopt extreme positions and the acquiring authorities in particular should be more realistic in terms of the money they offer. Then there wouldn't be so many cases at arbitration, " he said.