The note was sent following a meeting between Smith, a junior minister at the Department for Communities and Local Government, and Lloyd. In the letter the minister illustrates her lack of interest in the reform proposed by many in the profession.
Smith said architects should avoid trying to 'disassociate themselves from [title regulation]', and that in its present state the ARB is 'effective, efficient and careful'.
This has come as a sharp rebuff to the ARB Reform Group, which is made up of members elected to the ARB's board who have campaigned all year to see the work of the organisation pared back or even killed off.
The group has demanded that the government make changes to the 1997 Architects Act, which originally set up the ARB.
Some members of the group have argued that the registering of British architects should become a function of the RIBA.
But the letter dismisses these concerns. 'The ARB is- a minimalist body,' it states. 'Comparison with other regulators, statutory and non-statutory, clearly shows that it is both effective and efficient, and careful in its use of funds.
'Parliament is unable to instruct a regulatory body - one which it has set up as an independent body - on how best to administer its responsibilities.
'The legislation clearly established the ARB as a regulator, and endowed it with discretion to adapt to changing circumstances and public expectations.
'There would, it is true, have been other ways of going about the separation of roles. Some professions have voluntarily done it in-house. Others have needed encouragement, persuasion and in some cases legislation.
'Architects should take pride in the fact that they were among the first in the field and instead of trying to disassociate themselves from their chosen model of regulation, must seek to ensure that it evolves progressively for the benefit of the public and thus, ultimately, for themselves.'
Colin Brock, a member of the ARB Reform Group, said: 'It seems that the minister is in favour of the status quo, and this seems to be the way that she works.
'Next time, the delegation that goes to see the minister ought to be more balanced, so more than one message gets to her.'
'This will not defeat us,' Brock added. 'At least, it is extremely unlikely to. We must try by dialogue to win the arguments.'
However, long-term ARB critic Ian Salisbury disagreed. He said the letter was an improvement on previous correspondence from the government, which he claimed never even accepted that there was dissent.