'Key decisions will have to wait', Cameron says

"Before we do that we need to determine the kind of relations we want with the EU and that is rightly something for the next government to decide," he said.

"It is our sovereign decision and it will be for Britain and Britain alone to take," he added on the timing of the article 50 process, saying "all of the key decisions will have to wait" for the next government.

He also rejected calls for a new referendum.

He said that the decision taken by 51.9 percent of voters in last Thursday's referendum "must be accepted and the process of implementing the decision in the best possible way must now begin."

Cameron announced that the government had set up a new EU unit to implement Brexit and "explore objectively options for future relationships" with the EU and the rest of the world.

"This will be the most complex and most important task that the civil service has undertaken in decades," he noted.

Giving a insight into future planning, Cameron said that Britain wanted "the strongest possible economic links with our European neighbours" as well as with the US, Commonwealth countries, India and China.

He also said that "whatever the precise nature of our future relationship, we will want to continue with a great deal of our extensive security co-operation and to do all we can to influence decisions that will affect the prosperity and safety of our people."

"Britain is leaving the European Union but we must not turn our back on Europe or the rest of the world", he added.

The prime minister said the government would "fully involve the Scottish, Welsh and Northern Irish governments" as well as other authorities like the Gibraltar government and the London assembly in its plans.