The extension of the UK's job retention scheme "makes no difference" to the thousands of people who initially fell through the cracks, campaigners say.
Chancellor Rishi Sunak announced on Tuesday the scheme will now run to October covering 80% of workers' pay up to £2,500 per month.
But people starting new jobs who were not on the payroll before the 19 March cut-off date remain ineligible.
The government said the scheme was helping a quarter of the workforce.
HM Treasury said it had prioritised helping the greatest number of people as quickly as possible, whilst limiting fraudulent claims.
Some 7.5 million people are now covered by the scheme, which has cost £14bn a month.
Adam Chan, who helped start the New Starter Justice campaign group, which now has more than 9,000 members, said the government had "missed an opportunity to change the criteria" when it extended the scheme.
Initially, it was intended to support those already employed on 28 February but the cut-off date was later extended to 19 March.
The Institute for Employment Studies suggests more than 100,000 people may have fallen through the cracks because they started for their new employer in March but were not on the payroll before the cut-off date.
UKHospitality has told the House of Commons Treasury Committee between 350,000 and 500,000 workers in its sector would be ineligible.
Responding to a BBC Freedom of Information request, HM Revenue and Customs said it was unable to say how many new starters had failed to qualify, nor in what occupations.
'I have not got support'
Alison Craig had been working for four months in Christchurch, New Zealand, as an outdoor instructor with groups of school children.
She returned a month earlier than originally planned to take up a 12-month contract doing similar work in her native Scotland, in Fort William, but the job offer was withdrawn when lockdown began.
She cannot approach her old employer to be furloughed, as she had been in New Zealand, but she has been awarded £2,000 under a separate self-employed hardship fund being run in Scotland and is now claiming Universal Credit.
"It's disappointing this whole industry [of such seasonal work] has been forgotten," she said.
"My job was terminated due directly to coronavirus and I have not been able to get any furlough support."
'I've fallen through a loophole'
Daniel Scales moved from the Isle of Sheppey in Kent to take up a bar manager job in Cornwall, and he was working when the announcement pubs should close came on 20 March.
"When they announced the 80% thing, I thought I would be able to survive," he said. "But then I found out I had to have been on the books before 28 February. My heart was ripped out.
"When I heard what I was entitled to Universal Credit, it would not have covered my accommodation."
When the cut-off date was extended, Mr Scales asked his former employer if they would furlough him and was refused.
"For the government to say go back to your old employer was absolutely wrong. You move forward, people don't go back.
"I've been sofa surfing around friends since while I wait for Universal Credit to come through. I've lost a lot of dignity. I'm stressed all the time.
"I've fallen through a loophole and the extension of the scheme has done nothing for me."
'The extension is more daunting to me'
Head chef Rosa Webber started her new job at The Abbot's Fireside in Hythe, Kent, on 4 March.
"I'm paid monthly and I missed the cut-off," she said.
"I've applied for Universal Credit but I'm not entitled to anything because of my fiancé's earnings.
"Because I technically have a job to go back to, I'm not eligible for Jobseeker's Allowance either.
"It's crazy really but in some ways I'd be better off unemployed.
"My boss has been trying to show I was on the payroll but there's not really any wiggle room.
"The extension [of the scheme] seems more daunting to me because it's the prospect of not having a job or pay for another four months."
'I'm lucky I don't have a mortgage'
This year was due to be Tristan Gillett's sixth consecutive summer as a lifeguard at Whitsand Bay, Cornwall, working for the Royal National Lifeboat Institution (RNLI).
He said he was also ineligible for furlough and is now claiming benefits instead.
"I received my offer of employment on 2 March and my start date was 14 April, being paid monthly," the 24-year-old said.
"I have PAYE details going back five years to show the hours I would have been working and at what pay.
"Originally I was quite annoyed but the RNLI's only other option is to spend charitable donations to support us and that's not the purpose of the charity.
"I'm lucky because I don't have a mortgage."
HM Treasury said the Coronavirus Job Retention Scheme had "protected more than 7.5m jobs through this crisis" and had been "extended until October in order to continue supporting workers and employers across the UK".
"Those that aren't eligible for the scheme can make use of a number of other measures.
"These include our strengthened welfare safety net, giving councils an additional £500m to support the most vulnerable in our society and introducing mortgage-payment holidays and tax deferrals."