The union representing 2,300 Ottawa transit workers who went on strike 20 days ago is opposing the city's attempt to force members to vote on its latest contract offer.

The Amalgamated Transit Union confirmed it will submit by Tuesday a list of reasons why the offer shouldn't go to a vote.

The City of Ottawa had sent a letter to federal Labour Minister Rona Ambrose on Christmas Eve, asking her to call a supervised vote on the offer, under Sec. 108.1 of the Canada Labour Code.

Jim Haddad, secretary-treasurer of ATU Local 279, said Monday that OC Transpo transit drivers, dispatchers and maintenance workers voted 98 per cent in favour of a strike, and that mandate is still strong.

"They are saying to us, there's no reason for another vote and the mayor will not dictate to this membership," he said while about 20 workers nodded in agreement while picketing with him outside OC Transpo headquarters on St. Laurent Boulevard.

Over the weekend, a spokesman for Transport Minister John Baird said Baird and Ambrose were evaluating the situation and would respond early in the week.

Union members had walked off the job on Dec. 10 after failing to reach a contract agreement with the city. Talks between the two sides resumed briefly last week, but broke off again on Dec. 23. The union's website said the talks ended after the city "failed to show any flexibility" on its new scheduling proposal, the main issue of disagreement between the two sides.

The union has said the proposal takes away some of the flexibility for drivers to arrange their schedules to accommodate their personal lives. The city has said the proposal would be safer, fairer and more cost-effective.

Suspension of Parliament may have affected strike: MP

A Liberal MP in Ottawa suggested this weekend that the strike may be dragging on longer than it otherwise might because Parliament has been suspended until the end of January.

Gov. Gen. Michaëlle Jean prorogued Parliament on Dec. 4 at the request of Prime Minister Stephen Harper, avoiding a confidence vote on his Conservative government's controversial economic and fiscal update. MPs aren't scheduled to return to the House of Commons until Jan. 26.

Mauril Bélanger, Liberal MP for Ottawa-Vanier, said normally Parliament could enact legislation to deal with conflicts such as strikes.

"Now the people of Ottawa have one less option at their disposal than they would have otherwise," he said, adding that the threat of such legislation also normally keeps both sides conscious of the need to negotiate in good faith.