Some vehicle test centre staff have been on strike since last month

The group also claims that more than 10 small businesses, which run driving training schools, are facing closure unless the strike is called off.

Nipsa members began strike action last month at nine centres across the province.

It is part of a wider dispute over pay, which has began last December.

Glyn Roberts, of the federation, says it is unacceptable that there has been no dialogue between the union, Nipsa, and the government since March.

"We have already seen the loss of 25 jobs and I think it is only the tip of the iceberg," he said.

"We are going to see much more serious job losses, we are going to see many more small businesses face closure.

Nipsa has been involved in strike action since December

"The economy is going to suffer as a whole."

DVTA centres in Armagh, Craigavon, Lisburn, and Newry are unstaffed and no testing is taking place.

No testing is taking place at Belfast, Londonderry, Larne and Newtownards test centres, however some staff are providing an information service.

About 6,000 MoT tests a week, as well as practical driving examinations, are being affected by the industrial action.

Nipsa has been involved in strike action since December over what they said was the government's refusal to give civil service staff any cost of living increases in rates of pay since April last year.

The government has imposed a pay package which will add 3.67% to the wage bill of the Northern Ireland Civil Service.

However, union officials say that was part of a pre-agreed increment and takes no account of the rise in the cost of living.