An increasingly desperate Theresa May will try to shore up her flagging premiership with a raft of new policies aimed at young voters, as another cabinet minister refused to endorse her staying in office until the next election.

In an interview with the Observer on the eve of the Tory conference, which opens in Manchester on Sunday, communities secretary Sajid Javid declined to reply when asked if May should lead the Tories into the next election campaign.

Boris Johnson increases pressure on May with fresh Brexit intervention Read more

After a 40-minute discussion during which he lamented the way the last campaign had focused too much on Brexit and May herself, Javid laughed when asked the question, then stood up and declared: “I think we are out of time.”

Amid growing signs that cabinet discipline is breaking down and support for the prime minister is draining away, May will announce a series of policy changes in the hope of halting her party’s potentially disastrous loss of support among voters under 45. These will include freezing tuition fees, which are due to rise with inflation from £9,250 in 2017-18 to about £9,500 in 2018-19, while ministers look again at the system.

She will also announce that the earnings threshold at which graduates start to pay off their loans will be increased from £21,000 to £25,000, and will go up in line with earnings after next year. That will mean a saving of about £360 in 2018-19 compared with this year for graduates earning at least £25,000.

There will also be more help offered to aspiring homeowners, and to renters. As well as a £10bn expansion of the Help to Buy loan scheme, Javid will announce that all private landlords will be required to join a redress system that allows tenants to complain and see those in breach sanctioned. Javid will also oblige letting agents to be registered with a professional body and require them to meet a set of minimum standards.

In an eve-of-conference message, May said the policy announcements were “key parts of my plan to spread opportunity and build a better future for our country”. However, Conservatives will arrive in Manchester amid an air of gathering crisis not only over the prime minister’s ability to cling to office but also over her loss of support, particularly among younger voters.

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Polling by Opinium for the Social Market Foundation published by the Observer shows that more than twice as many voters under the age of 45 now think Jeremy Corbyn’s Labour party is “on their side” than believe the same about the Tories.

Commenting on the figures in an article on theguardian.com, Phillip Lee, a minister in the justice department, says the Tory party is now a “huge turn-off” for most younger people.

Also commenting on the party’s problem with younger voters, Paul Masterson MP said his party had to make sure it didn’t “get to the stage where it is seen as an analogue party in a digital age”.

He said: “If the party wants to win over young voters, it must become a dynamic force for modern, inclusive, open and – yes – liberal conservatism that speaks to their most basic of wants: the chance to buy their own home, a decent job, a safe environment for their families and a fair crack at fulfilling their potential.”

The foreign secretary, Boris Johnson, fuelled suspicion that he wants to replace May as leader when he used an interview in the Sun to make further provocative demands over Brexit, including an insistence that the transition period announced by the prime minister last “not a day longer” than two years.

Johnson’s remarks appeared to break a cabinet agreement that the precise duration of transition be left open. The foreign secretary also appeared to suggest that there could be no role for the European court of justice during a transition period, which he knows Brussels will refuse to accept.

While May wants to focus the conference on her domestic agenda, it seemed increasingly likely on Saturday night that issues of leadership and Brexit would dominate. The Liberal Democrat leader, Vince Cable, will lead a mass anti-Brexit protest outside the conference.

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Johnson’s interventions have been met with a mixture of concern and withering contempt by key EU leaders even as the tone of the negotiations improved following May’s speech in Florence. The German chancellor, Angela Merkel, is understood to be interested in the idea of a transition period but worried by the uncertainty in the UK over what is being sought, both in its length and its terms.

Matti Maasikas, the deputy prime minister of Estonia, which currently holds the rolling European council presidency, voiced the widely held belief that hopes of gaining the support of leave voters ahead of the scheduled 2022 UK general election were driving those seeking a two-year limit on the transition ending in 2021.

“Am I mistaken,” he asked, “if I say that so far these dates, the possible numbers on the duration, have more to do with British domestic considerations?”

The length of the transition period should, he added, be determined by how long it takes the UK to get its new systems of controls at the border ready, and by whether it remains “beneficial to the EU”.

Maasikas also insisted that those, including Brexit secretary David Davis and Johnson, who believe the UK would be outside of EU law and the remit of the European court of justice during that period would face a wholly united and opposed EU27.

“Should the single market arrangement be there, it is the whole package, with the acquis [EU law],” he said. “Preserving the integrity of the single market, this is one of the crown jewels of EU integration. I expect the EU to be very rigid about this.”

Asked whether the EU would open talks about a transition period at the European council summit later this month, as the UK hopes, Maasikas, said: “No.” He added, though, that it was up to the EU’s chief negotiator to ask leaders for a mandate to do so.