Welsh devolution is regarded as an "experiment", said Carwyn Jones
Wales' First Minister Carwyn Jones says the understanding of devolution within Whitehall departments is "variable".
Mr Jones gave evidence before MPs on the Welsh Affairs Select Committee sitting in London.
The committee is carrying out an inquiry into the relationship between Wales and Whitehall.
Mr Jones also defended the current system by which Welsh laws are made and the "absolutely essential" role of the Wales Office in that process.
Mr Jones told MPs: "I think it's fair to say that some Whitehall departments are better than others. The response from Whitehall departments is variable in terms of understanding."
He said he thought officials and civil servants in UK government departments had a better understanding of the Scottish devolution settlement than the Welsh one.
Mr Jones said: "Scotland has been regarded as something separate but Wales has been regarded as just an experiment in devolution... I think there is still scope for improvement."
The first minister said there needed to be greater awareness at Whitehall that even if a bill is of a non devolved nature there may be parts of it which have an impact on Wales, and gave the Welfare Reform Bill as an example.
He told MPs that the present Legislative Competence Order (LCO) system of making Welsh laws is robust and has led to closer working between Wales and Whitehall and improvements over time.
LCOs are the means by which the assembly's requests for new powers are scrutinised in turn by AMs and MPs.
Once an LCO is approved at Westminster the Welsh Assembly Government is empowered to pass its own laws in the subject area covered by the LCO, such as education and training, or vulnerable children.
'Got in the way'
These are known as assembly measures and are enforceable by the courts in the same way as acts of parliament.
Mr Jones said that the role of the Wales Office is "absolutely essential" when dealing with LCOs and that there hadn't been any occasions when the Wales Office "got in the way".
He argued the civil service in Wales can cope with the requirements of the process, something he believes is proved by "the robustness of legislation".
The Welsh Assembly Government's most senior civil servant, Permanent Secretary Dame Gillian Morgan, also gave evidence.
She once said she was shocked by the lack of commitment to devolution within Whitehall departments, but now insists the situation has improved.
She said the UK's top civil servant, Sir Gus O'Donnell, has provided leadership and makes sure that devolution is on the agenda.
Dame Gillian Morgan admitted that the civil service in Wales has fewer staff compared with Whitehall, resulting in capacity issues, but added that they have been changing the way they work to create "a different model of civil service."
Explicit about impartiality
In the past, she said, work in Whitehall was done by senior staff but Wales had few people of seniority.
Dame Gillian Morgan said: "I've now put more people in positions of seniority.
"Sir Gus O'Donnell holds a meeting of the top 200 (civil servants) and in the past Wales could only send two civil servants but now more are able to attend."
Dame Gillian also told MPs secondments for civil servants between Wales and Whitehall are more frequent and that she actively encourages the secondment of Wales' civil servants to Westminster or Brussels.
She said she hoped any change of Government in Westminster would not impact on the work of the civil service or on the secondment scheme because the civil service code is explicit about impartiality.