The practice released a statement responding to criticism from members of the assembly over its role in the scheme, where costs have risen by £14m to £40m.
It said: "RRP rejects being made a political scapegoat for a catastrophic failure properly to manage the project."
The practice said it was not considering legal action at present.
Welsh assembly finance minister Edwina Hart told the assembly on Tuesday that Rogers would be unable to deliver the building within the £13.8m construction budget, bringing the total cost of the project to more than £40m. Rogers' contract was immediately terminated.
The firm said the minister's claims were "plainly untrue". It added that the assembly had discouraged competitive tendering and this had led to the acceptance of bids from local contractors that were more expensive than those from Continental competitors.
The dispute is likely to delay the project by up to 12 months, which will take the completion date a year beyond assembly elections in 2003.
The assembly will now push forward with a new procurement process.
The spokesman also praised management contractor Skanska, saying that the company bore no blame for the problems.
Skanska will continue working on site for up to two months, so that the project can be safely put on hold until a new lead contractor is found.
It is believed that the assembly has encouraged Skanska to retender for the management contractor's role.
Hart said that a final decision on whether to proceed with the building would be made "in the light of new proposals".
The Conservative Party, which is opposed to devolution, said the project should now be scrapped.
But a Welsh government source said: "The three pro-devolution parties want the project to push ahead.
"Ultimately this is a big political decision – we don't want to see the £8-9m that has already been spent go down the drain."
The source added that another troubled capital expenditure project, the £92m Millennium Centre in Cardiff Bay, was unlikely to be affected by the debacle. Assembly members were to vote on the issue yesterday and acting deputy first minister Jenny Randerson has recommended the project should be given the go-ahead.
But the source conceded that the difficulties over the assembly building were unhelpful, given the feeling in north Wales that Cardiff had too many prestige projects.