Labour is trying to win over Liberal Democrat voters by highlighting its illiberal drugs policy

The opposition party's stance on drugs hasn't gone down well with some activists

The Labour advert (The Labour Party)

Labour has launched a new campaign to win over Liberal Democrat voters by attacking their party for being “soft” on drugs.

A new poster released by the party this week brands the liberals “soft on crime, drugs and thugs” and references their policy of ending prison sentences for drug possession.

Nick Clegg called for decriminalisation of drug use in a joint conference with entrepreneur Sir Richard Branson early last month.

But Ed Miliband has ruled out moving towards a decriminalised system, despite claims by observers that similar moves have led to impressive harm-reduction results in other countries.

The vast majority of voters Labour has won over since 2010 are former Liberal Democrats, according to data compiled by the British Election Study.

The group is seen as key to the party’s chances of victory in May.

Labour’s attempt to retain these voters by highlighting its illiberal credentials confused and dismayed some of the party’s activists and supporters, however.

“Trust the Labour Party to attack one Lib Dem policy that is actually desperately needed. The war on drugs has failed,” tweeted Lily Jayne Summers, a Labour activist from Wales.

Fergus Boden, a student who lives in Edinburgh, said he was a “potential voter in a swing seat”.

“I live in what's predicted to be marginal Labour seat. Why are they making it harder by pandering to the right?” he tweeted.

The criticism of the poster comes days after the party released a commemorative mug celebrating “controls on immigration” which took fire for alleged xenophobia.

The British Election Study shows Labour has gained roughly net zero voters from the Conservatives since 2010 and probably needs disillusioned Liberal Democrats to form a majority.

The party has also lost a solid chunk of this group to the Green Party in recent months amid complaints that Ed Miliband is not taking Her Majesty’s Opposition a radical enough direction.

“I had left the Labour party to find the values that I thought that it once stood for, and I found them, in the Greens,” former Labour member Jack Monroe wrote in the Guardian newspaper last week.