The United Kingdom (UK)'s decision to quit the European Union (Brexit) demonstrates that ASEAN's slow pace of regional integration is correct and that top-down integration is not sustainable, says CIMB Group Chairman Datuk Seri Nazir Razak.

"Brexit will be sobering for those of us championing ASEAN integration and a great reminder that ASEAN should move at a pace that works for the majority of the people of ASEAN.

"It (Brexit) is also a vindication of ASEAN's steadfast focus on trade and investment and avoidance of single currency and other steps that have political implications," he said in an interview with Asia House, the leading pan-Asian organisation in the UK.

The vision of the ASEAN Community, as detailed in the 2007 ASEAN Charter, is to create an integrated and cohesive economy for entire ASEAN with a free flow of trade, goods and services and skilled labour and investments.

But, when the ASEAN Economic Community (AEC) was established at the end of 2015, not all of the measures had been implemented.

The new AEC Blueprint 2025, agreed in 2015 in Malaysia, aims to achieve the vision of having an AEC by 2025 in which all 10 ASEAN member states are both economically integrated and fully integrated in the global economy.

But it has stop short of advocating a single currency.

Nazir also said that the lack of clarity on the likely outcome of Brexit negotiations means it was difficult to make any forecast.

"(For) those of us who have already invested in the UK, (we) will obviously have to bear some pain from the immediate drop in the sterling and valuation of assets generally.

"Hopefully, it is temporary and holding on for the long-term will prove the right decision," he added.

Echoing other leading Asian business and government figures, Nazir was optimistic that Brexit would lead to strengthening of trade and investment ties with Asia.

"We expect the UK to quickly demonstrate greater eagerness for closer ties with the rest of the world and that could bring opportunities for us in Asia and especially for countries like Malaysia that have maintained strong socio-economic ties," he added.