Long-serving SNP MP Pete Wishart has said he is standing as House of Commons Speaker to pursue a "reforming" agenda that will modernise Parliament.

The Perth and North Perthshire MP announced his candidacy amid speculation current Speaker John Bercow plans to quit the role in the summer.

Wishart joins Conservative MP Sir Edward Leigh and Labour's Chris Bryant in expressing interest in the job.

Traditionally, the role of Speaker comes with a peerage, but he told STV News he would "never" accept one.

Wishart has served his constituents of Perth and North Perthshire since 2005, having previously been elected to the since-abolished seat of North Tayside in 2001.

He only narrowly won re-election in 2017's snap general election, defeating Tory candidate Ian Duncan by just 21 votes.

Explaining why he wants to stand, Wishart said: "I'm the longest-serving member of parliament in Scotland, I have experience in practically every front-bench responsibility, I'm about to go on the House of Commons Commission.

"I know procedure like the back of my hand in this place.

"What I want to do is bring forward a reforming, far-reaching agenda that will totally transform this place, bring it into the 21st century and really change the nature of the way that we do business.

"So, I'm looking forward to participating in this contest."

Pressed by STV's Westminster correspondent Kathryn Samson on if he would accept a peerage, having previously described the House of Lords as "bloated" and "ermine-coated", the SNP MP vowed not to.

He said: "There's a whole load of things I've called the House of Lords and I think I could give this as an exclusive to Scottish Television: if I am successful I pledge never to take a place in the unelected House of Lords.

"In fact, that's one of the things I want to address as Speaker. One of the things in my ten points is we have to look at reforming Parliament.

"We can't have part of the parliamentary state devoted to appointees, cronies, donors, aristocrats and Church of England bishops."

Wishart's ten-point manifesto includes bringing in electronic voting, abolishing the dress code, allowing clapping, allowing MPs to address each other by name rather than constituency, extending proxy voting, and bringing in "21st-century working hours".

The Speaker of the House is expected to be impartial, meaning the Speaker has to effectively resign from his party.

Wishart has faced a backlash from some online supporters of independence accusing him of attempting to come "part of the establishment".

But the MP told STV: "As we're leaving Westminster - the Scottish National Party members of parliament - maybe it's a parting gift to them to help fix some of the procedural issues.

"If we will be asked to vote in any future Speaker's elections, it's good that there's a whole range of candidates available to do that, and SNP members of parliament will have an SNP candidate to support."

His position was backed by First Minister Nicola Sturgeon, who said: "For as long as the SNP is in the House of Commons, we should be trying to make it work as well as we can."