In last Thursday's poll, the Conservatives went from 331 seats to 318 while Labour increased its number of MPs from 232 to 262.
Duff, who lost his seat in the last European elections, told this website the result increases the chances that the UK will bid to stay in the customs union.
Duff, now a visiting fellow at the Brussels-based European Policy Centre, said, "This is a move that would command a majority in the new House of Commons as well as the agreement of the EU 27."
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Also commenting on the outcome of the election, former Nato Secretary General Anders Fogh Rasmussen said Scandinavian countries "have a great deal to lose from a messy divorce with the UK."
He added, "We must speak up for our interests, and for a future relationship that keeps our markets as open as possible.
"Businesses and governments alike are still grappling with the uncertainty and complexity of these negotiations. We regret the UK's decision to leave, but we must not seek to punish Britain. We should find the best partnership possible.”"
Baroness Ros Scott, ALDE party Vice-President and former President of the Liberal Democrats, commented, "This result shows that the British people are rejecting the Tory vision for a hard Brexit and that the new government must rethink."
Former UK Europe Minister Denis MacShane told this website, "The British election as predicted has settled nothing. Britain has neither leadership nor a political project for organising its economic, public finance, and social problems, still less for deciding next steps in its relationship with Europe.
"The assumption that an early election can solve the problem is far from proven. Tory MPs who have just arrived in the Commons or held onto their seats narrowly will not want to rush for an early election. The Scottish Nationalists are major losers in the election with the Conservatives, Labour and the Lib Dems all returning to win seats in Scotland.
Sir Nigel Sheinwald, former British Ambassador to the EU, said, "Businesses in Britain and Europe must make their voices heard on Brexit - in favour of a negotiated departure, not a car crash; and for an economically and politically close future relationship."
He added, "Whatever feelings we have about Brexit, businesses need clear judgment and the best available information on which to base their future strategies."