OTTAWA - Stephen Harper's vaunted Senate reform agenda is in jeopardy, with Newfoundland becoming the fourth province to insist that provincial consent must be obtained to change Canada's upper house.

In a letter to the prime minister, Newfoundland and Labrador Premier Danny Williams joins Ontario, Quebec and New Brunswick in contending that Parliament cannot unilaterally reform the Senate.

Williams asks that Harper withdraw both Bill S-4, which would impose eight-year term limits on senators, and Bill C-43, which would create a process for electing senators.

"If you are intent on Senate reform, then it must be done correctly,'' Williams says in the letter.

"Any changes should be carefully considered by both (federal and provincial) constitutional orders of government in the context of a national public debate. The current piecemeal and unilateral approach does not suffice.''

Harper, whose western Tory base has long advocated overhaul of the Senate, has declared reform of the unelected chamber to be a top priority.

But Liberals have been lukewarm to the term-limit proposal and they are opposed outright to Senate elections. The number of provinces weighing in against Harper's proposed reforms and the vehemence of their objections could now give the Liberal-dominated Senate justification for killing S-4, which is currently stalled in a Senate committee.

Harper's minority government may have trouble winning approval for C-43 in the House of Commons, where all three opposition parties have signalled their opposition to it. But should it make it to the Senate, the Liberal majority could determine its fate as well.

The fate of the term-limit bill should become clear on Wednesday when the Senate's legal and constitutional affairs committee is scheduled to give it clause-by-clause examination.

Celine Hervieux-Payette, Liberal leader in the Senate, said Monday that she needs to consult her colleagues before determining the course of action they'll take. But she said senators, who are supposed to represent Canada's regions, will have to take seriously the provinces' objections.

"For me, it's hard to say that I cannot attach any importance whatsoever to the (views of) 11 million Ontarians, seven million Quebecers and the Maritimers,'' she said.

"I guess actually it's important to consider that it's more than half of the population of this country now that stands in the way of the prime minister and a prime minister who really was bragging about the fact that he was going to be the one that will listen to provinces.''

She noted that one of three territories, Nunavut, has also weighed in with objections to Parliament unilaterally changing the Senate.

While the Liberal-dominated Senate could simply kill S-4, Hervieux-Payette said recommending that the bill be referred to the Supreme Court is "one of the options.'' The court could be asked to advise whether provincial consent is necessary.

Peter Van Loan, the government's House leader and minister responsible for democratic reform, doubted Liberal senators will go so far as to kill S-4, which he said would fly in the face of public opinion and amount to a snub of their own leader, Stephane Dion. Dion has endorsed the idea of term limits but has proposed increasing the term to 12 to 15 years.

"I don't they'll kill it. I think they'll just engage in more delay,'' Van Loan said in an interview.

Noting that Liberal senators have been dragging their feet on the three-clause bill for over a year already, he added: "Nothing would surpise me in terms of their creativity and ingenuity in finding new ways to delay.''

The Tories maintain that imposing a term limit on senators, who can currently serve for up to 45 years until the age of 75, is a minor change that does not require provincial consent. Van Loan noted that the government's view is backed by some of the country's foremost constitutional experts as well as some provinces.

The Tories also contend that provincial consent isn't necessary to create a process for electing senators. Technically, C-43 doesn't change the constitutional requirement that senators be appointed by the prime minister, although he would in future appoint only those who win election.

In his letter to Harper, Williams argues that imposing an eight-year term limit would alter the essential characteristics and powers of the Senate. And, citing a 1980 Supreme Court ruling, he says that means it requires a constitutional amendment approved by at least seven provinces representing 50 per cent of the population.

Williams says C-43 raises even more grave concerns, for it is clearly a deliberate attempt to avoid the constitutional requirement for provincial assent while altering the method of selecting senators."