Nicola Sturgeon, Scotland's first Minister and leader of the Scottish National Party, delivers her party's election manifesto in Perth, Scotland, Britain May 30, 2017. REUTERS/Russell Cheyne

LONDON (Reuters) - Scottish leader Nicola Sturgeon said on Friday she still expected Prime Minister Theresa May’s Conservatives to win a majority at next week’s national election, but was no longer certain it would increase.

Sturgeon told the BBC that if the Conservatives did fail to win an outright majority, her pro-independence Scottish National Party would consider supporting a “progressive alliance” of other opposition parties on a case-by-case basis.

“The most likely outcome here is a Tory (Conservative) victory, but a Tory victory no longer certain of an increased majority,” she said, discussing her reading of opinion polls.

The Conservatives’ lead has narrowed with just a week before the vote on June 8, potentially weakening May’s position ahead of the start of formal talks to leave the European Union.

Should the Conservatives lose their parliamentary majority, that would add fresh turmoil to British politics.

“If parliamentary arithmetic allowed it, I would want the SNP to be part of a progressive alternative to a Conservative government, not as a coalition, but on an issue by issue basis,” Sturgeon said.

That means she would support Jeremy Corbyn’s Labour Party and work with the Liberal Democrats, both of whom oppose Scottish independence from the United Kingdom.

Sturgeon’s party is expected to easily win the election north of the English border, but to lose some of the 54 seats it holds, out of the 59 allocated to Scotland in the national parliament.