The Liberal Democrats must capitalise on Tim Farron's "powerful" speech with hard graft on the campaign trail if the party wants to make gains at next year's elections, according to Sir Ming Campbell.

The former Liberal Democrat leader told IBTimes UK the activists would now have "do the business" on the doorstep after Farron's keynote address at the party's annual conference in Bournemouth on 23 September.

"Speeches in conference halls are one thing – getting out there and doing the business on the doorstep, that's something else," Campbell said. "But no one who was here today could be anything other than encouraged and enthused by Tim Farron and by the nature of the leadership he is going to provide."

The Liberal Democrat peer spoke immediately after Farron attacked David Cameron for ignoring his humanity and being stuck in "media management mode" after the prime minister promised to take up to 20,000 Syrian refugees from UN camps over the course of this parliament, which comes to an end in May 2020.

"That is one of three areas which it looks very clear now that Tim Farron is going to concentrate on," Campbell added. "On Europe, a powerful case for that; on refugees, a powerful case for that, and right on the forefront, a powerful case for more social housing so people can enjoy the security which having their own home necessarily brings."

Farron's speech marked the end of the Liberal Democrat conference, which gave the left-of-centre party an opportunity to take stock and revitalise itself after being reduced to just eight MPs at the general election.

Nick Clegg, the former deputy prime minister, resigned after the disastrous result and was in attendance for Farron's speech. The new leader particularly praised Clegg for his post-election speech, when the Sheffield Hallam MP warned liberalism was under threat in the UK.

"You know, there are those that would like me to take this opportunity to distance myself from the past five years, to say it was all some dreadful mistake, to say: 'I disagree with Nick.' But I don' I won't," Farron said. "I came into politics to change things, to make a difference, to make people's live better. And to do that, you need the power to bring about the change.

"There is nothing grubby or unprincipled about wanting to win. Nothing noble about defeat – losing sucks, losing robs you of your change to make people's lives better. What's the point in being right if you never get to put you policies into action? So I am proud of what we did in government and I am determined that we will return to government."