Prime Minister Gordon Brown has defended the new EU treaty, saying it brings an end to institutional change "for the foreseeable future".
Mr Brown signed the treaty hours after the official ceremony last week
He also told MPs they would get the chance to debate "in the fullest detail" the bill being published to bring the EU Reform Treaty into UK law.
But David Cameron said Mr Brown would "not restore trust in British politics" unless he holds a referendum.
He also accused Mr Brown of "dithering" over not attending the treaty signing.
Referring to the bill being published on Monday, he said he would ensure there was enough time for the Commons to have "the fullest opportunity to consider this treaty and the deal secured for the UK ratification".
He said the bill would also bring in measures to ensure "no government can agree without Parliament's approval to any changes of European rules that can in any way alter the balance of power between Britain and the EU".
"Any future amendments to the treaty would have to be ratified by an Act of Parliament so Parliament would have absolute security that no future change could be made against their wishes," he added.
But Mr Cameron asked how the prime minister could "say that having just signed up to an all-encompassing constitution that transfers powers from Westminster to Brussels" he will not hold a referendum.
"It's this sort of approach that makes you look shifty and untrustworthy," he said.
"Don't you see that far from getting you out of your troubles, denying people a referendum is digging you in deeper. This treaty is obviously the constitution."
He claimed European leaders "now see the prime minister in the same light as the British people - not as the strong leader he posed as in July", but as "weak, dithering, second rate would be a bonus for this prime minister, and not straight with people".
Acting Lib Dem leader Vince Cable asked if Mr Brown's late arrival in Lisbon was "incompetence, discourtesy or dishonesty or a combination of the three".
"The whole episode has reflected badly on Britain as a country and not just on him," he said.
On Thursday the prime minister missed the official ceremony, attended by 26 other EU heads of state, blaming a diary clash with his twice-yearly grilling by senior MPs on the Commons liaison committee.
The foreign secretary attended in his place, and Mr Brown signed the treaty three hours later.
KEY LISBON TREATY REFORMS
Creates new European Council president
New foreign policy supremo to increase EU profile
Commissioners reduced from 27 to 18
Removes national vetoes in around 50 policy areas
Voting weights between member states redistributed
No reference to EU symbols such as the flag and anthem
Treaty faces referendum in Ireland and must be ratified by all other EU parliaments
Downing Street has dismissed the criticism as a "fuss over nothing" as Mr Brown had eventually signed the treaty in public.
The treaty has proved politically controversial, as it was drawn up to replace the EU Constitution, which was rejected by French and Dutch voters at referendums in 2005.
Most Conservative and some Labour MPs argue that, as the Labour government had promised a referendum on the constitution, it should do the same for the treaty which they say is substantially the same.
But the government says it is very different, and does not require a referendum. It says changes are either minor and procedural, and Britain has negotiated "opt outs" for other changes, where necessary.
In a wide-ranging update on the summit's conclusions, Mr Brown said the UK would send 80 policemen and judicial officials to Kosovo, after the failure of UN-sponsored talks to bring independence to the UN-administered province of Serbia.
He said member states had agreed to discuss Iran's nuclear ambitions again in January.
And he warned: "Iran has a choice, confrontation with the international community, leading to a tightening of sanctions, or if it changes its approach, a transformed relationship with the world, from which all would benefit."
He praised the "significant progress" made at last week's climate change summit in Bali and said Europe had to help step up funding to the developing world to adapt to global warming.