They say one of the toughest speeches to make in the Commons is the Leader of the Opposition responding to a Budget. You’ve only found out what the spending cuts and commitments are during the Chancellor’s speech, and very often you have no idea what a clever-sounding new policy really means. Minutes later, you’re on your feet and somehow words are coming out of your mouth.

But an even harder job, perhaps, is responding to an announcement from the Government when you’re only looking after the Opposition party while it elects a leader. You don’t know what the new boss’s policies will be, but you still have to offer some kind of response to what the government is unveiling.

This is the tricky job that Harriet Harman is trying to fulfil at the moment as interim leader of the Labour party. There is a (rather small) list of quite different characters standing to lead the party, and a debate about what it should say and do in order to start winning elections again. But in the meantime, there are plenty of bills and spending cuts that ministers will try to whisk through Parliament, and Labour must say something. It’s Harman’s job to work out what that something is.

She gave a warm and witty response to the Queen’s Speech on behalf of her party this week, and appears to be enjoying running Labour for a short period of time. She knows how this works, after all: Harman took over in 2010 between the party leaving government and it electing a new leader.

This experience from one of Labour’s veteran MPs is pretty valuable when the government has decided that now is the time to introduce any controversial legislation. The only really organised Opposition force in the Commons at the moment is the SNP, and they still have only 56 MPs. Number 10 reasons that while the Labour party and the Lib Dems are trying to elect new leaders and Tory backbenchers are in a fabulously good mood after winning the election, the government can get on with passing bills on a tiny majority.

The interim leader has decided she has four priorities for her short tenure: strong, effective opposition, stability and unity, learning the lessons of the party’s defeat and a good leadership contest. She is helped by the party’s formidable chief whip, Rosie Winterton, who is popular and respected, but also slightly feared within the party.

Appointments in David Cameron's Tory government Show all 7 1 /7 Appointments in David Cameron's Tory government Appointments in David Cameron's Tory government Amber Rudd: Energy and Climate Change Secretary Wins a big promotion after increasing her majority in Hastings and Rye despite once describing her constituency as a “bit depressing”. The former banker and financial journalist is considered a moderate Eurosceptic Appointments in David Cameron's Tory government Priti Patel: Employment Minister (attending Cabinet) Former party press officer and now the Witham MP is rewarded for her forceful performances during the election campaign. She is on the right of the party and a Eurosceptic. Ms Patel has called for the return of hanging Appointments in David Cameron's Tory government John Whittingdale: Culture Secretary Having never been a minister in his 23 years as an MP John Whittingdale’s elevation to the Cabinet is meteoric. But his appointment sends a message to Tory backbenchers that preferment is possible even for those who may have given up hope (and be tempted to rebel) Getty Appointments in David Cameron's Tory government Anna Soubry: Minister for Small Business Not long ago the former defence minister feared she would not even be an MP but now she has a key role in the Department for Business and the right to attend Cabinet Appointments in David Cameron's Tory government Sajid Javid: Business Secretary Rising star tipped as Britain’s first prime minister from an ethnic minority. Son of a bus driver, he grew up in two-bedroom flat in Bristol. After university he joined Deutsche Bank. Parliamentary aide to George Osborne before becoming Treasury minister and Culture Secretary Appointments in David Cameron's Tory government Greg Clark: Communities Secretary Thoughtful moderniser who grew up in Middlesbrough where his father and grandfather were milkmen. Was a special adviser before entering Parliament in 2005. In previous ministerial posts he drew up plans to devolve powers to cities Appointments in David Cameron's Tory government Matthew Hancock: Cabinet Office minister and Paymaster General A former aide to George Osborne before becoming an MP in 2010 election. Hancock has had a meteoric ministerial rise

Even those who disagree with Labour’s stance on certain issues should want a good strong Opposition, as it has a constitutional role in scrutinising legislation and trying to stop any stupid policies from becoming law.

The party seriously struggled at the beginning of the last Parliament when ministers were announcing big benefit cuts and reforms, as it firstly had no leader to set direction, then it had a new leader who set up a long and laborious policy review which he then didn’t bother to make much use of.

Ed Miliband commissioned so many working groups that the MPs initially in charge of the policy review lost track of them. He even had a weighty book on policy written by a think tank, which also didn’t make much of a difference to Labour’s final offer. That policy review meant that Labour went for even longer without an idea of whether it should oppose or support controversial government measures.

This time round, Harman seems to be setting policy without waiting for the bothersome new leader and their cumbersome review. She has already ditched the party’s opposition to an EU referendum, and said that Labour is “sympathetic” to lowering the benefit cap for workless families from £26,000 to £23,000.

The benefit cap policy was something the party discussed behind the scenes over the past week, knowing the Tories would try to set a trap for Labour on the issue. The Shadow Cabinet has become a forum again in which people debate matters, rather than just turning up and pretending they all agree on everything.

Harman has also been in touch with the leadership candidates, although one campaign says it was not consulted before the benefit policy changed, and says that “nothing Harriet does now is set (or written) in stone”, which suggests that there may be confusion ahead on some big policies. The Tories would love it if there was confusion, with Labour flip-flopping around on controversial issues. David Cameron made much of the party’s previous struggles to respond to the benefit cap when it was set at £26,000. He’ll do the same this time if the party ends up changing its mind.

The Tories are also lying in wait with a grin the size of Shere Khan for Labour to lumber its way to a clumsy response on the new, surprising proposals on trade unions. We had long known that the Tories wanted to introduce minimum turnouts for union votes on strike action, but the proposals introduced in Wednesday’s Queen’s Speech include forcing union members to “opt in” to a levy to fund a political party as part of their membership fees, rather than opting out.

Harman has already said that changing party funding should not be “rigged in favour of the Tory party”, but her party will need to tread a fine line if it is not to appear as though its MPs are just opposing reforms because the unions sponsoring them have told them to.