Former British envoy to Tehran, Sir Richard Dalton has criticized the West's response to Tehran Declaration on Iran's nuclear fuel deal as disappointing.

Referring to the deal reached in Tehran between Iran and Turkey and Brazil to swap the Islamic Republic's nuclear fuel and better known as Tehran Declaration, Dalton said that the deal should have been built upon.

Dalton said the deal was unfortunately not well handed, adding that "The Tehran Declaration should have had a more positive reception and what it offered for the future should have been explored".

Dalton said: "Building upon the declaration should be pursued as a tripartite strategy to resolve the dispute over Iran's nuclear program".

Dalton's stance was shared by former Prime Minister Gordon Brown's advisor on non-proliferation, Baroness Shirley Williams, who, last week, criticized the West's response to the Tehran Declaration as "deeply unwise".

“Instead of taking it seriously and suggesting that a further negotiation might bring about a real move by Iran towards putting most of her low-enriched uranium into safe situations, the West simply dismissed it,” Williams told the British parliament.

Dalton, himself also said the West's strategy should also include engaging with Iran on long-term issues with a “wider agenda”. He is now an associate fellow at London's Chatham House, a policy think tank.

There should be a “vigorous attempt” to start the inclusive agenda and discuss matters of concern on both sides that was envisaged in the approach last October, he said.