Holyrood candidates from Scotland's three main parties are afraid of "rocking the boat" by endorsing Brexit, the Scottish Vote Leave head has claimed. Former Labour MP Tom Harris, who is leading the Scottish campaign to take Britain out of the EU, said he knew of candidates running for the SNP, Scottish Labour and the Scottish Conservatives who privately backed Brexit but did not want to admit it. While Mr Harris said he had only spoken to a small number of anti-EU candidates, he also claimed those in question were standing in "winnable" Holyrood seats. "A lot of them just don't want to rock the boat and draw attention to themselves," he said. He added: "I know there are candidates standing for the Scottish Parliament who feel as I do, that we should be leaving the EU on June 23. "But they are inhibited by their own party's line on the EU, and don't want to say anything publicly at least until May 5, and possibly not even after that. That is fundamentally undemocratic. "It is absolutely essential that we have the opportunity to grill our candidates and get an honest answer from them on whether or not they will actually vote themselves to leave or remain. It is not enough to say it is a separate election from the referendum." Mr Harris said he hoped party leaders would "agree to untie the gags of all of their candidates and allow them to speak freely." Responding to the remarks, an SNP spokesman said: "Quite why Mr Harris thinks Scots will be attracted by an anti-Europe campaign in which he is joined by the likes of Nigel Farage, Boris Johnson and other right-wing Tories is anyone's guess. "SNP candidates and members are perfectly able to express their views on the issue - and we look forward to Scotland as a whole voting strongly to stay in Europe." A Scottish Labour spokesperson said the party "will be campaigning to remain in the EU as we believe it's in the best interests of families all across the country," adding: "It will be for individual MSPs to decide how they will vote in the EU referendum, but the vast majority will be campaigning for an In vote. Understandably however, our candidates are more focused on the Scottish Parliament elections on May 5." A spokesman for the Scottish Conservatives said: "Ruth has been clear that members and candidates can take any position they like on Europe. Indeed, our justice spokeswoman has already detailed her support for leaving the EU." Download: The STV News app is Scotland's favourite and is available for iPhone from the App store and for Android from Google Play. Download it today and continue to enjoy STV News wherever you are.