Writing in a BBC blog, Thompson outlined some of the corporation's plans for covering the month-long election period, with Prime Minister Gordon Brown today confirming May 6 as the election date.
Thompson said that it is vital for the BBC to "provide a strong and independent place where the big debates can take place - free from political or commercial influence".
The BBC's coverage plan includes The Daily Politics show on BBC Two being extended from 30 to 60 minutes for the entire length of the election campaign.
Alongside its planned debate between the three prime ministerial candidates, the BBC will also host nine 'cabinet contender' debates, which Thompson said would "provide a unique opportunity for the public to compare and contrast what each party has to offer on the issues that matter".
The BBC will also air two election debate programmes in Scotland, three in Wales and 12 40-minute regional debates around England towards the latter stages of the campaign.
"This could be one of the closest and therefore most ferociously fought elections in living memory. With the stakes so high for the political parties, it would not be surprising if they were in contact about how we are covering what they do and say," said Thompson.
"Whilst we will always take seriously any accusations or questions about our even-handedness and accept any mistakes if we get things wrong, we will show neither fear nor favour in how we report the election.
"It is vital that the BBC is able to provide a strong and independent place where the big debates can take place - free from political or commercial influence. In this public space, everyone can have access to the lifeblood of healthy democratic debate - impartial news and information.
"The strength of our impartial public service broadcasting, combined with a strong newspaper tradition, is what makes us distinctive from most democracies around the world."
Alongside chairing the BBC's Prime Ministerial Debate, David Dimbleby will also continue hosting Question Time, including a live show immediately after the leader's discussion concludes.
Jeremy Paxman will quiz politicians from all sides on Newsnight, with additional shows planned for Saturdays, and the BBC's political editor Nick Robinson will track the leaders' progress on the campaign trail around the UK.
On election night, the BBC will have a presence at "every single count" to provide comprehensive results coverage on TV, radio and online platforms.
Dimbleby will host the Election Night programme on BBC One, joined by Paxman, Robinson and Jeremy Vine with the new-look Swingometer.
Emily Maitlis and Peter Kellner will provide seat-by-seat analysis, while Fiona Bruce will deliver regular news updates and Andrew Neil will conduct on-the-spot interviews.
Speaking about the coverage, BBC News director Helen Boaden said: "With the polls indicating this could be the closest election in decades, the BBC's coverage will be vital in helping the public compare and analyse the policies and choices provided by the parities and candidates standing for election. Our coverage will be clear, authoritative, and most importantly impartial."
The BBC's chief political advisor Ric Bailey recently revealed that the British National Party could appear on Radio 4's long-running Today programme in an effort to maintain political balance around the election.