Plans for a new four-runway hub airport in the Thames Estuary have been described as fanciful and extreme by the leader of Essex County Council.

In comments that echo the opposition to "Boris Island" already expressed by both Kent County Council and Medway Council, Essex leader Cllr David Finch (Con) said the schemes envisaged were unrealistic, impractical and too costly and disruptive to deliver.

Instead, the government should consider a third runway at Heathrow and sensible growth at Stansted.

"As a country we don't have the time or the money to waste on unpractical or undeliverable schemes. A third runway at Heathrow should not be ruled out as an option.

"It is the elephant in the room: the most viable, affordable and practical option to improve UK aviation capacity. The Commission – and the government – needs to take a pragmatic approach on this in the economic interests of the country."

He added: "Some of the plans from the Mayor of London to shut down Heathrow in its entirety and build a giant airport elsewhere – whether at Stansted or on a floating island in the Thames - seem like extreme and fanciful ideas.

"We need to get real on aviation and not focus on pie in the sky options that would hoover up costs twice the size of the UK's annual defence budget."

A report setting out the authority's views "Flights of Fancy: Getting Real On Aviation" states Stansted can help add immediate capacity and new routes to the London and south east airport system within its existing permissions.

Meanwhile, two former trade ministers have criticised the delay in deciding how best to increase air capacity in the UK.

The warning has come from Lord Digby Jones and Lord Mervyn Davies, who have told Sir Howard Davies, the man leading the government's review, that Britain is missing out when it comes to exports and investment.

In a letter to Sir Howard, who is due to publish interim findings this December on various options, the pair say: "We are increasingly concerned about the gradual decline in Britain's global aviation capacity when compared with our European competitors and the negative impact this is already having on our economic competitiveness.

"For British business to flourish in a global economy, we need to export goods and services and we need to attract inward investment to and from new, as well as existing, markets. In neither respect can we do so if our airport system is not optimised."

Final recommendations are not expected to be made until after the next general election, leading some to claim the timing is designed to avoid politically contentious proposals.