A referendum on further powers for the Welsh assembly will not take place this year, it has been confirmed.
Secretary of State for Wales Cheryl Gillan said she cannot pass the necessary legislation in time due to circumstances inherited from Labour.
She said the aim is now to hold the vote before the end of the first quarter of 2011.
In a letter, Mrs Gillan blamed First Minister Carwyn Jones and former Welsh Secretary Peter Hain for the delay.
She added that the UK coalition government remains "committed" to the referendum.
"Your decision that the date and question should not be considered until after the General Election has meant that we have not yet submitted a question to the Electoral Commission, which has confirmed that it will need at least 10 weeks to carry out its assessment and then report," she wrote in a letter to Mr Jones.
"This inevitably leads to a position where we cannot lay the referendum order by the 17 June 2010.
"Both you and I and the deputy first minister have discussed a possible timetable for the referendum, taking account of all the stages that need to be gone through to prepare for it.
"In the light of our discussion, we have agreed that we should aim for a referendum to be held before the end of the first quarter of 2011."
On 17 February Mr Jones wrote to Mr Hain to notify him of the Welsh assembly's resolution of 9 February, calling for a referendum on further law-making powers for the assembly.
This gave the Secretary of State 120 days to either lay a draft Order in Council under the Government of Wales Act before Parliament, or refuse to do so and give reasons.
The wording of the referendum question would have to be "tested" by the Electorial Commission and the process would have to go through the UK parliament.
In a statement a Welsh Assembly Government spokesperson said: "We note the Secretary of State's announcement on the referendum.
"The first minister and deputy first minister will be having further discussions with her about the precise timetable for the referendum to take place in 2011 in line with One Wales.
"The coalition parties remain committed to the One Wales agreement to campaign for a successful outcome in the referendum."
Plaid AM and deputy group leader Helen Mary Jones said: "We made it a priority to get a referendum to clear this mess up before the end of this assembly term, and of course I am pleased that this will be delivered."
Liberal Democrat Roger Williams, MP for Brecon and Radnorshire, said his party had argued for a referendum to take place as soon as possible, but it was "essential" the process was carried out correctly "so that any result is not open to challenge".