Ukip has been handed a boost after media regulator Ofcom proposed including it on the list of "major parties" for May's general and local election campaign - guaranteeing it more air time in England and Wales.

But the Greens look set to miss out despite having an MP and regularly outscoring the Liberal Democrats in recent opinion polls.

Ofcom said its initial view was that a stunning surge by Ukip that saw it top May's European elections, win its first two Commons seats and overtake the Liberal Democrats as the third party in opinion polls was sufficient to promote it to the list.

Putting the proposals out for consultation however, it said it believed that both the Greens and Traditional Unionist Voice (TUV) in Northern Ireland had "not demonstrated significant past electoral support in general elections" to justify inclusion.

Parties on the list are guaranteed at least two party election broadcasts (PEBs) on each of the TV and radio channels covered by the system - which does not include the BBC.

Ofcom's Broadcasting Code requires that "due weight must be given to the broadcast coverage of major parties during the election period".

It does not directly affect which party leaders are invited to take part in live TV debates, which is an editorial matter for each broadcaster in direct negotiation with the parties.

But Ofcom rules require broadcasters to ensure all coverage, including debates, complies with rules concerning due impartiality.

The Green Party is already angry at being excluded from the proposed line-up of those set-piece head-to-heads and leader Natalie Bennett said she was "deeply disappointed by this draft Ofcom ruling, not only for itself, but for the damage it risks doing to British democracy.

"The media regulator has failed to grasp the fast-moving, fluid state of British politics today, and that fact that voters are seeking out the choice of real change," she said.

"Ofcom should not be making that option harder to find, but ensuring that voters have the chance to hear and judge the full range of political options today.

"It is also important to note how Ofcom is ignoring the strong support for the Green Party in particular sections of the community, particularly the young and students.

"Their engagement in the political process is vital for the future, and they will rightly expect to hear their views represented and explored in the mainstream media."

Tory MP Zac Goldsmith, a prominent environmentalist, joined criticism of what he called a "disgraceful, indefensible decision by Ofcom".

At present, only the Conservatives, Labour and the Lib Dems are on the UK-wide list but the dramatic rise in support for other smaller parties and the prospect of another hung parliament has heightened calls for more rights to put their case.

The SNP enjoy similar status in Scotland along with Plaid Cymru in Wales and the Alliance Party, the Democratic Unionist Party, Sinn Fein, the Social Democratic and Labour Party and the Ulster Unionist Party in Northern Ireland.

The consultation is open until February 5 with a final decision due in early March.