Transport Minister Keith Brown announced his bid to become deputy leader of the SNP.

Mr Brown echoed statements made by leadership contender Nicola Sturgeon on the prospect of another referendum and said they enjoyed a close working relationship.

Ms Sturgeon said she will not endorse any candidate and will ­allow the party to make a decision on who the deputy should be.

Mr Brown said he joined the party around the same time as Ms Sturgeon and has worked in her department as Transport Minister for two years since she became Infrastructure Secretary.

He said: "I've known Nicola Sturgeon since we both joined the party in the 1980s worked in the same portfolio for two years. I believe it is a close and good relationship.

Mr Brown said he had the support of more than half the SNP ­parliamentary group. However, the election will be decided by the membership, which has more than doubled since the referendum to more than 60,000.

On a future referendum, Mr Brown added:

"You can't put a time on it, it depends on ­circumstances and the people."

Dundee MP Stewart Hosie has also announced his candidacy for deputy leader and said he wanted to ­increase the number of SNP MPs to increase pressure on the UK Government.