Natalie Bennett: Everything's changed, and the broadcasters have to recognise that

The 2015 general election is already shaping up to be very different from that of 2010. Five years ago, commentators were speculating that the financial crisis would be like many that came before, after which there would be a recovery as usual. There was little understanding of the interlinked economic, social and environmental crises whose shape and seriousness are clearer by the day. Listen to the broadcasters and the regulator as they try to justify their plans for the 2015 election leaders' debates, and you'd think nothing had changed.

Yet if you talk to voters, look at the opinion polls, look at the membership of parties (the Green party is up more than 120% last year, to more than 32,000 in England and Wales alone), and talk to people around the country, and it is clear that it has.

Voters are seeking alternatives to the failed austerity policies of the three business-as-usual parties. They understand that more than three decades of the same economic priorities that have put company profits before the interests of the public have failed.

It's that cultural shift – along with our performance in the European elections last year and polls (around the same level as the Liberal Democrats, and at 19% among under-25s) – that demands the debates are not restricted to four parties who can only offer us more of the same.

Of course I'm calling for the Green party's inclusion – and while he clearly has his own political interests, so is David Cameron, his case bolstered by its evident fairness (and the backing of 275,000 petition signatories) – but there is a strong argument for a broader structure that allows in other anti-austerity voices.

It is telling that the old politics is represented by very familiar-looking faces, delivering the usual Punch-and-Judy debates. When we three female leaders got together last year, we talked about what we agreed on. We not only talked the politics of the future, but also started to consider what it could look like.

Without that voice – of the new, anti-austerity politics, with its new style – the leaders' debates will be failing British voters and British democracy.

Natalie Bennett is leader of the Green party

Nicola Sturgeon: Ofcom needs to catch up with what's happened in Scotland

It is not often that I see eye to eye with George Osborne, but a few days ago I found myself agreeing with him on the subject of the general election debates.

He made the point that if Ukip are to be included in these debates then other parties should be too. He may not have meant the SNP but, even if inadvertently, Osborne was caught telling the truth.

Following the Scottish independence referendum, the political landscape has changed utterly. The SNP is now the third biggest political party in the UK in terms of membership – and more and more people across Scotland are putting their trust in us to stand up for them at Westminster.

So when it emerged that the broadcast regulator Ofcom is failing to even consult on the SNP as a major party in the UK in its review of parties ahead of the general election, this signified a major failure to understand the changing nature of politics. The fact that Ukip is included only crystallises how out of touch the regulator is with developments in Scotland.

Similarly, the Guardian's involvement with a consortium seeking to exclude the SNP from a digital debate with "the UK's five main political parties" – which isn't true whether in terms of number of MPs or size of membership – is just as disappointing.

With a larger membership that the Liberal Democrats and Ukip combined, and more elected MPs than Ukip, the case for including the SNP is undeniable. The SNP's general election campaign coordinator, Angus Robertson, has written to Ofcom to query its undemocratic and illogical decision. Broadcasters – and the broadcast regulator – have a duty to be impartial in their election coverage. To exclude the SNP would be a failure to deliver these democratic duties.

Along with Plaid Cymru and the Green party, a strong team of SNP MPs at Westminster will work to do everything possible to tackle inequality and bring about sustainable economic growth – and we must be given the opportunity to deliver our message.

At the general election, it is imperative that the SNP is seen and Scotland's voice is heard.

Nicola Sturgeon is first minister of Scotland and leader of the Scottish National party

Leanne Wood: We must have a debate for the age of devolution – and that includes Plaid Cymru

The proposed exclusion of Plaid Cymru from the televised leaders' debates once again highlights the flawed approach of the broadcasters and regulators as they refuse to reflect the reality of the UK's democracy.

It is flawed for three primary reasons. Firstly, their definition of a "major party". Plaid Cymru has had continuous presence at Westminster for the past four decades. We have been a party at times instrumental in the context of minority governments. It is likely that we will find ourselves in a key position after the next UK election in the event of another hung parliament. That means our proposals for the rebalancing of power and wealth throughout the UK could have implications for all.

Secondly, the broadcasters and regulator have come to an unsatisfactory conclusion because they refuse to recognise the multinational nature of the British state. The notion of a single, homogenous UK entity is long gone in an age of devolution where so many domestic affairs are decided at national, not state level. This has yielded different voting patterns and political outlooks and should be reflected in any UK-wide debates among the parties.

Thirdly, there is something disingenuous about labelling the proposed televised debates as "prime ministerial". It is a helpful label to use if seeking to exclude parties not seeking to enter Downing Street but again, this convenient adoption of an American idea is not appropriate for a parliamentary election. These are leaders' debates and may prove decisive in who ends up with the keys to No 10.

That is why Plaid Cymru should be included. It is a question of basic democracy. It isn't so much about my party gaining electoral exposure but about people having the opportunity to scrutinise us and to have access to the full range of available opinion to make an informed choice.

Leanne Wood is leader of Plaid Cymru