Committee Chair, Dr Hywel Francis MP, said:
"The arrival of democratic devolution for Wales over the past decade has been the biggest constitutional change for Wales since 1536. Our inquiry must be seen in this historical context.
"Ministers and senior civil servants at both ends of the M4 need to be more coordinated, strategic and transparent in their development and delivery of devolution with a much higher priority given to awareness raising of Welsh devolution in Whitehall.
"Welsh Ministers and Welsh civil servants of both governments should be much more pro-active in achieving this."
The Committee makes a number of recommendations to improve the relationship between Wales and Whitehall;
A broad review of how intergovernmental relationships are coordinated is required. The Joint Ministerial Committee should meet on a regular basis and ministers at all levels should be alert to the consequences of policy and legislation on devolved areas.
The Cabinet Office should take lead responsibility for devolution strategy in Whitehall. At present, no strong centre in relation to devolution exists within the Government and this hinders a coordinated approach.
After an initial burst of concentration, Whitehall has lost a focus on the devolution settlement and too often has displayed poor knowledge and understanding of the specificities of the Welsh settlement. The Civil Service needs more consistent training and clear department-by-department focus on retaining devolution knowledge and understanding.
The Welsh Assembly Government should have the confidence to interact with Whitehall and to promote areas of good practice.
The Cabinet Secretary and the Permanent Secretary to the Welsh Assembly Government should give evidence annually to the Welsh Affairs Committee to ensure devolution remains on the agenda.
Reform of the Barnett Formula is required. The current financial settlement does not appear sustainable and a new arrangement needs to be built on an agreed and enduring basis which is demonstrably fair and sensitive to the particular circumstances of Wales.