SNP Westminster leader Angus Robertson has claimed that the Prime Minister and Scottish Secretary have lost control of the Scotland Bill process.
Mr Robertson said that the Bill falls short of the cross-party Smith Commission agreement and has written to Mr Cameron outlining details of how it does so.
Earlier this week Mr Robertson challenged Mr Cameron at Prime Minister's Questions (PMQs) on the issue of the Scotland Bill, with Mr Cameron saying they had delivered on all of the promises made to the people of Scotland.
Meanwhile Scottish Secretary David Mundell said that the latest Scotland Bill, the second in three years, will be the last and will provide ''a stable devolved settlement to which the alternative is independence".
Mr Robertson said today: "Both the Prime Minister and the Scottish Secretary have their heads buried in the sand on this issue and have now lost control of the Bill process. First we have the Prime Minister announce that there will be amendments to the Scotland Bill, and simultaneously have David Mundell saying that it is this or independence.
"It is clear to the vast majority of Scots - only 9% believe the Vow has been fulfilled - and also the architect of the Vow, Gordon Brown, that the Scotland Bill is not delivering on what was promised to the people of Scotland."
He added: "On issues of welfare, employment and the constitution, the Scotland Bill does not deliver on what was promised in the Vow or what the people of Scotland voted for at the ballot box in May. This is backed up by the Scottish Trade Union Council, the Scottish Council for Voluntary Organisations, Carers Scotland and Enable Scotland, who have all said that the Bill does not deliver enough. Even the House of Commons library explicitly states that the Bill does not deliver on Smith in full.
"The situation that we are now in is one where David Cameron thinks that he and his one Tory MP in Scotland can dictate to everyone else what is devolved to the Scottish Parliament and what is not – the Prime Minister should just do what he promised and deliver the Smith Commission package in full."
At PMQs on Wednesday Mr Robertson asked: ''When will you deliver on the promises that you made to the people of Scotland?''
Mr Cameron replied: ''We have delivered on all of the promises that we made.
''We said we would introduce a Scotland Bill, we introduced a Scotland Bill.
''We said unprecedented devolution on taxes, there's been unprecedented devolution on taxes.
''We said we'd provide those welfare powers, we've given those welfare powers."
On Thursday Mr Cameron said: "We promised in the Vow to devolve historic powers on tax, we have, historic powers on welfare, we have, and we promised to put the future of Holyrood beyond doubt, and now we do that.
"So the Vow has been delivered, but there was also another vow that was made, and that was to say that this referendum settled the issue, in the words of the former first minister, for a lifetime, potentially a generation.
"And that's what I believe, that's what he said, and that's what we should stick to. Let's deliver the powerhouse parliament, but let's recognise the Scottish people spoke and they said, 'Let's stay together.'"