The former Conservative business and Scotland Office Minister, Lord Malcolm Offord, has defected to Reform UK.
He was unveiled by Nigel Farage at a rally at the Macdonald Inchyra hotel in Falkirk on Saturday.
Lord Offord was the serving Treasurer of the Scottish Conservatives and served on the Lords front bench from 2021 until 2024.
He told the rally he planned to stand down from the Lords and campaign as a candidate for Reform in the 2026 Holyrood elections.
Announcing his defection, Lord Offord accused the Conservatives of "giving up" on Scotland.
He called the party "parochial, not political" and described them as a "party without a vision".
"I'm concerned for Scottish politics, very concerned about what happens in Scotland," he said.
"And that's why I'm leaving the Scottish Conservative Party, because the Scottish Conservative Party, I believe, have given up on Scotland and, ladies and gentlemen, I can't do that."
He added: "From today, for the next five months, day and night, I shall be campaigning with all of you tirelessly for two objectives.
"The first objective is to remove this rotten SNP government after 18 years, and the second is to present a positive vision for Scotland inside the UK, to restore Scotland to being a prosperous, proud, healthy and happy country."
It is not possible to renounce a life peerage, but peers can resign their membership of the House of Lords.
Members of the House of Lords are disqualified from becoming members of the Scottish Parliament under legislation passed earlier this year.
Reform has one MSP at Holyrood; the former Conservative, Graham Simpson, who defected to the party in August.
Farage said he was "delighted" to welcome Lord Offord to Reform, describing his defection as "a brave and historic act".
He added: "He will take Reform UK Scotland to a new level."
Scottish Labour deputy leader Jackie Baillie called Reform a "party of failed Conservatives playing political musical chairs".
She said: "This defection proves what we already know, Reform aren't even Tories in disguise anymore, they are just Tories - the same Tories that broke the immigration system, collapsed the economy and left working Scots to pay the price.
"This isn't change - it's the same failed politicians and failed ideas trying to divide our country."
Lord Offord, who founded investment firm Badenoch and Co, was made a life peer in 2021 under Boris Johnson.
He had previously donated almost £150,000 to the Conservative party.
Following his peerage, he became Baron Offord of Garvel, of Greenock in the County of Renfrew, and was appointed as a junior minister in the Scotland office.
He also served as served as a minister of exports from 2023 until the general election in June 2024.
He was previously director of the Vote No Borders campaign during the 2014 Scottish independence referendum.
The group attracted controversy after being forced to withdraw a cinema advert which claimed Scots would lose access to the Great Ormond Street Hospital in London in the event of a Yes vote.
The hospital complained about the message, saying it did not endorse the content and was not consulted prior to it being broadcast.
Lord Offord also stood as a Conservative list candidate for the Lothian region in the 2021 Holyrood election, but finished fifth and did not gain a seat.
Malcolm Offord isn't a household name, but Reform's Scottish operation will be very happy to have him on board.
He's held a number of UK government ministerial posts, and was a serving Conservative frontbencher in the House of Lords.
He wants to be a candidate at the next Holyrood election. And he'll bring both business and political experience to the party.
Taking to the stage in Falkirk, he complained about the "monopolitics" of Labour and the Conservatives.
He seems to have fallen out of love with his old party.
The crowd here was delighted to welcome him, despite his very recent Tory past.
But, some of his old colleagues aren't too sad to see him go.
One Scottish Conservative insider messaged me calling him a "treacherous snake".
Ouch.