The appointment of Jim Murphy has failed to reverse Labour's historic decline in Scotland, a new poll has found.

Labour remain lodged on just 27% - their lowest recorded level ever - with the SNP 19 points ahead on 46%, according to a YouGov poll for the Times.

If repeated in May, the findings suggest the SNP would pick up at least 48 new seats with Labour reduced to a rump of just nine.

Just as worrying for Labour is the apparent collapse in perceptions of their new Scottish leader. Fifty-one per cent now say Murphy is doing badly as leader with just 26% saying he is doing well. This is down from 33% last month.

By contrast a large majority of voters approve of the job being done by Nicola Sturgeon. Sixty-two per cent say she is doing well as SNP leader, with 29% disagreeing.

On the positive side, Murphy's campaign strategy of warning voters that a vote for the SNP is a vote to keep David Cameron in Downing Street does appear to have been heard by voters.

Asked if they had to choose between a Labour government and a smaller number of SNP MPs and a Conservative government and a larger number of SNP MPs, 45% chose the former and 34% the latter.

However, support for a Labour government remains lukewarm in Scotland. Just 37% said a Labour government led by Ed Miliband would be better for Scotland than a Conservative government led by David Cameron. A significant chunk of 28% of voters said it would make "little difference" either way.

And despite playing on fears of another Conservative government, support for the Tories in Scotland has actually increased since Murphy became leader.

Today's poll finds the party on 18% up three points from last month. If repeated at the election, the poll suggests the Tories could even increase their share of the vote on five years ago.

Murphy has come under repeated attack from nationalists in recent months for being a so-called "red-Tory".

This perception will not be helped by Murphy's decision today to launch a new campaign poster based on the Tory "tax bombshell" from 1992.

At the printers to see Labour's latest campaign poster come off the press, "SNP Barnett Bombshell costs 138,000 jobs" pic.twitter.com/RSaLdJEQar — Jim Murphy (@jimmurphymp) March 12, 2015

The poster, which claims that "SNP plans will cost 138,000 jobs", is based on Labour claims that the SNP's devo-max plans would cause an additional £6 billion worth of cuts.

In further echoing of Conservative campaign tactics, Murphy is now pushing for the Green Party to be included in this year's televised debates.

"Enjoyed the first debate of 4 Scottish party leaders tonight at Glasgow University. The Greens should be included in TV debates to make it 5," he tweeted last night, adding "Dear @BBCScotland & @WeAreSTV it's great you're organising Scottish party leaders election debates but why not invite Scottish Greens as well," this morning.

Murphy's latest campaign mirrors the tactic first pursued by David Cameron earlier this year in an attempt to get the Greens included in the UK-wide televised debates.

Conservative election strategists believe that including the Greens in the debate will split left-leaning voters away from Labour.

Labour's Scottish woes have also been worsened by persistent Tory attempts to get the party to rule out any post-election deal. Ed Miliband last night told the BBC that the prospect of any such deal was a "nonsense".

However, support for such a coalition remains strong in Scotland. Fifty-four per cent told YouGov that Miliband should not rule out doing a deal with the party.