In a post-summit Commons statement on 26 June 2012, Mr Clegg told MPs that the next generation will need 30% more water, 45% more energy, and 50% more food.

BBC: Clegg laments outcome of Rio+20 summit

That's followed by a statement by the prime minister reporting back on the European heads of government summit - and following last week's emergency Commons debate, his words will be closely scrutinised by his own backbenchers.

BBC: Week ahead in Parliament

But opening an estimates day debate on preparations for the summit, on 28 February 2012, Labour MP Joan Walley told the Commons it was essential for the prime minister to represent Britain.

BBC: MPs urge PM to attend Rio+20 summit