Who is @IDS_MP? Not who you think, David... Cameron mentions spoof Iain Duncan Smith account on Twitter as he defends benefit cap

In an apparent response to the PM's tweet @IDS_MP replied: 'Chin chin Dave. Round mine for a Pimms later?'

He famously claimed that the trouble with Twitter was that "too many tweets might make a twat", and today David Cameron once again demonstrated the dangers of the micro-blogging site for politicians after he mentioned a spoof Iain Duncan Smith account as he backed a controversial new benefit cap.

The Prime Minister's account, which is followed by 366,000 people, published a tweet saying: "We're rolling out a cap on Benefits today - @IDS_MP and I are determined to make work pay, and help the UK compete on the #GlobalRace."

Unfortunately for the PM, the @IDS_MP account is not connected with the Work and Pensions Secretary, and indeed spends most of its time mocking the minister.

Sample tweets from the account include: "I've always supported a Mansion Tax. Your Tax buys my Mansion. Chin chin!", and "A thrifty way to keep cool in this heat wave is to dab the ice from your Champagne bucket onto your forehead."

At the beginning of this month the mystery user behind the account wrote: "A 15% increase in MPs pay is a disgrace. Has anyone seen the price of Foie gras and Armand de Brignac...we need at least 25%"

Surprisingly perhaps, the mistaken tweet, which has been since been retweeted 409 times and 'favourited' 134, remains on the Prime Ministers feed.

In an apparent response to the PM's tweet @IDS_MP replied: "Chin chin Dave. Round mine for a Pimms later?"