UKIP are now leading in Thurrock and are only just behind the Conservatives in Rochford and Southend East, according to YouGov.

YouGov makes it clear the information is not based on a ‘constituency poll’ or a 'forecast'. It is a nowcast, modelled on detailed demographics and voting intention from over 150,000 interviews nationwide.

The YouGov nowcast, taken on Friday lunchtime, suuggests that in Thurrock, which is currently held by the Tories, Ukip are now on 44 per cent, with Labour in second on 38.2 per cent and the Conservatives back in third on 34.2 per cent.

In Rochford and Southend East, again a constituency currently held by the Tories, the Nowcast suggests Ukip are now just two points behind with YouGov claiming the vote is "too close to call".

The Conservatives lead on 42.9 per cent, Ukip are second on 41.1 per cent with Labour third on 30.8 per cent.

The Nowcast - which is not based on detailed constituency data or any forecast, comes after a major leadership debate in which seven party leaders, including Ukip supremo Nigel Farage, were quizzed by a live audience on ITV.

There is better news for the Conservatives in Castle Point where they are leading Ukip, according to YouGov's Nowcast. It is suggested the Tories are in front on 41.9 per cent with Ukip on 33.4 per cent and Labour on 28.5 per cent.

YouGov’s Nowcast uses a mathematical formula with data from across the country to predict voting intentions.

The Nowcast gives candidates an upper and lower range of percentage of votes, these statistics show the upper range.