This new poll should have the Brexit campaign very worried

• ORB phone poll: Remain 55 / Leave 42
• Men, Tory voters, and the elderly are all now more likely to vote against a Brexit

A new poll is worrying reading for people campaigning for Britain to leave the EU.

Not only does the ORB poll show another comfortable lead for Remain campaign, but it also suggests social groups that were once very likely to back a Brexit are now leaning towards the status quo option.

The phone survey - published on Monday for The Telegraph newspaper - said that Remain had a 13 point lead over the campaign for Britain to leave the 28-nation bloc (55 > 42%). These results continue a recent trend of phone polls giving sizable winning margins to the Remain campaign with less than a month to go.

And even more concerning for Brexiteers is that ORB's findings show how social groups that were once more likely to back a Brexit are now deserting the cause.

A breakdown of the poll's findings reveals that 57% of respondents who voted Conservative in last year's election intend to vote for Britain to remain. In March, this number was just 34%. Tory supporters appear to be abandoning the Brexit mission in their droves.

POOL New / Reuters

The ORB poll will make encouraging reading for Prime Minister David Cameron and Chancellor George Osborne, who have been campaigning for Britain to remain in the EU.

Britons aged 65 and over were previously regarded as the most likely social group to support the country leaving the EU. However, 52% of respondents who fall into this bracket said that they intended to vote for Remain. In March, just 34% of this group said this.

This swing extends to men, too. Around 55% of male respondents told ORB that they would vote for a Brexit when surveyed in March. Two months on, 55% plan to vote for Remain.

This is really bad news for the Brexit campaign. Being behind in the race is one thing, but failing to retain your key voter groups is another.

This latest development comes as the chances of a Brexit are being downplayed by polling analysts and bookmakers alike.

Matt Singh's most recent referendum forecast said that the probability of Britain voting to leave on June 23 was less than 20%.

Betting companies including William Hill and Ladbrokes are also offering odds of 7/2 of a Brexit taking place next month. This translates to a probability of around 22%.

Last week, Britain's premier polling firm YouGov criticised phone polls for overstating public support for Britain to remain an EU member state.