Ben Wallace: "Judicial review"

Speaking outside the Court of Session Mr Wallace said: "This supposedly neutral executive seems intent on only helping one side in this debate.

"This is unfair to other MSPs who want to ensure that any amendments to Mike Watson's Bill would make 'good' law. After my request for the same executive assistance was refused, I decided that any such bias should be stopped, and that Lord Watson should look elsewhere for help with his Bill."

The Conservative MSP for north-east Scotland said he was not treating the challenge as a party political issue but was acting in his capacity as a member of the parliament.

'Great injustice'

He added: "I am seeking judicial review of the legitimacy of help for Mike Watson and also, if it is legitimate, on their refusal to help me."

The Scottish Countryside Alliance said it would support Mr Wallace in his fight to overturn a "great injustice".

A spokesman for the alliance said: "The executive cannot have it both ways, be neutral and at the same time offer assistance to one MSP but not to others.

"It smacks of hypocrisy and undermines the credibility of parliament."

A Scottish Executive spokesman said: "We await the legal challenge. We will consider our response accordingly."