Team GB's competitors have been set an official medal target of at least 48 medals across 12 sports in London, which would represent their best performance for more than a century.

UK Sport, which has invested more than £300m of taxpayer and Lottery funding in Olympic and Paralympic sport over the past four years, promised British athletes would do better than in Beijing. In 2008, they also finished fourth in the medal table, with 47 medals across 11 sports including 19 golds.

The chief executive Liz Nicholl said UK Sport was not erring on the conservative side of expectations by picking the figure of 48 from a projected range of 40 to 70 medals that had been arrived at after close consultation with 25 of the 26 Olympic sports. Because UK Sport does not fund football, it is not included in the projections. But Nicholl added that somewhere near to the middle of the range, around 55 medals, was "probable" and said 40 would be a failure. Twenty Olympic sports have targeted medals in London, compared with 14 in Beijing.

"At least 48 is what we're saying. Nobody here can say it will be 54, 55 or 56. It's possible but not probable that it'll be at the outliers, it's more probable that it'll be towards the middle. But our commitment is to 48," said Nicholl.

A study from Sheffield Hallam University this year predicted that Team GB would win 56 medals, including 27 golds.

Peter Keen, the UK Sport special performance adviser who oversaw the creation of its "no compromise" system, said matching the performance in Beijing would be no small feat given that cycling would not be able to equal its haul in 2008 due to rule changes.

Cycling has been tasked with delivering six to 10 medals, rowing with six, boxing with three to five, swimming with five to seven and athletics with five to eight. At the other end of the scale, success for volleyball would mean winning a single match. In return for record investment in elite sport ahead of a home Games, UK Sport promised government a top-four finish with more medals in more sports than in Beijing, and sports minister Hugh Robertson said it was well placed to deliver.

"Team GB goes into London 2012 as the best prepared team in British history," he said. "Expectations for medal success are high but I am sure our athletes will rise to the challenge."

Over the past four years, UK Sport has received more than £500m in lottery and exchequer funding. Nicholl said the organisation had "moved on" since Beijing and was much better at working with sports and accurately predicting their potential medal haul.

Robertson defended the ambition to field athletes in every sport in London, despite the tension it had created with UK Sport's "no compromise" approach, which ruthlessly targets investment in medal chances. The Guardian revealed earlier this year that some sports that are unlikely to qualify for the Rio Games would see their funding cut altogether.

"You are put under very considerable pressure by the International Olympic Committee to put home teams into every sport to drive ticketing revenues," said Robertson. "That is a very particular dynamic for a home Games. For the Rio cycle, it will be a very straightforward no compromise approach and there will be sports funded at a lower level."

UK Sport also unveiled its final Mission 2012 analysis, which has been monitoring the progress of Olympic and Paralympic sports since before Beijing. Fifteen sports have an overall "green" rating and 13 an "amber" rating.

Taekwondo, which has been mired in controversy created by the decision to select Lutalo Muhammad over the world No1 Aaron Cook, admitted the affair had impacted negatively on its medal chances.

"The high-profile 'noise' generated around this matter has been an unwanted and significant distraction for the team at an important time," it said. Taekwondo is targeting between one and three medals from its four selected athletes.

UK Sport chair Sue Campbell confirmed that funding for the Rio cycle would be dependent on improvements to the governance of certain sports in the wake of a string of selection rows and complaints of opaque procedures and lack of transparency. "That has to change and it is a challenge for all of us. There will be a new set of criteria in next set of funding agreements where we will be addressing that and having much more transparent and accountable selection procedures," added Robertson.

The sports minister also revealed that he had engaged in a bet with his opposite number in Australia, Kate Lundy. If Team GB wins more gold medals, Lundy has promised to row across Eton Dorney in a British vest. But if the Australians triumph, Robertson has said he would dribble a ball around Australia House in a "rather nasty terylene hockey shirt".

In Beijing, one of Robertson's predecessors, the former Labour sports minister Gerry Sutcliffe, won a similar bet with his Australian counterpart.