A new unionist party founded by Better Together activists will field candidates in May's Scottish election for voters who feel "let down" by Scotland's mainstream pro-Union parties.

The Unionist party – full name "A Better Britain – Unionist party" – was founded by a group of Glasgow-based activists who met through the cross-party Better Together campaign to keep Scotland in the UK during 2014's independence referendum.

One founding member, John Mortimer, told BuzzFeed News that "a few dozen" unionist activists have joined together with the intention of getting at least one MSP elected to the Scottish parliament in May to "challenge the complacency" of the three main pro-Union parties.

"Politics in this country has changed forever – it used to be left and right but for the foreseeable future it's going to be unionism and nationalism," said 26-year-old Mortimer. "I don't think the mainstream unionist parties have responded to that.

"They're still arguing against each other, splitting the vote, and they're never going to come together because they're the big UK parties. We have to take that step ourselves, take a strong stance on the union, and give people a truly unionist option in May."

In 2014, the Better Together campaign united the Conservatives, Labour, and the Liberal Democrats and has been credited as a major factor in Scottish Labour's near-wipeout in last year's general election. Since the referendum, all three parties have argued for varying levels of devolution to Scotland.