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Jackson Carlaw, the acting leader of the Scottish Conservatives, has declared he will campaign to succeed Ruth Davidson, as the contest formally began.

Carlaw, the then deputy Scottish Tory leader, became interim leader after Davidson unexpectedly resigned last August, citing family pressures and her long-standing unhappiness over the UK party’s stance on Brexit.

The overwhelming favourite, Carlaw announced on Monday on Twitter he would stand and said: “We must take the fight to Nicola Sturgeon and the SNP, broadening our platform and diversifying our party.”

Jackson Carlaw MSP (@Jackson_Carlaw) As nominations open for leader of the Scottish Conservative & Unionist Party this morning, I can confirm I’ll be standing.



We must take the fight to Nicola Sturgeon and the SNP, broadening our platform and diversifying our party.



I’m ready for the fight. Join me #TeamJackson pic.twitter.com/CllpDXZzJT

He told the Sunday Times he thought the Tories would need to ditch some “precious” policies to compete more aggressively in the centre ground as “blue collar Conservatives”, although he failed to specify which.

He is expected to face competition from Michelle Ballantyne, an MSP who is the party’s social security spokeswoman, who said she believed there needed to be “a contest and not a coronation”. Ballantyne said she would stand if she won nominations from 100 party members.

A remain voter who has since enthusiastically backed Boris Johnson’s Brexit stance, Carlaw been backed by several senior colleagues, including Murdo Fraser, a former leadership candidate who lost out to Davidson in 2011. Liam Kerr and Rachael Hamilton, two other frontbench MSPs, are to chair his campaign.

There had been speculation that Adam Tomkins, the constitutional affairs spokesman, could stand but Tomkins said he backed Carlaw.

The Telegraph has reported party grandees would prefer to avoid a contest, arguing a three-month long leadership campaign will detract from their efforts to oppose Nicola Sturgeon’s government, with 15 months left to the next Holyrood election.

The Tories became the second largest party at Holyrood under Davidson’s leadership, winning 31 of its 129 seats in the 2016 election.

Nominations close at noon on 17 January.