Around 34,000 households have received the payouts to help with soaring energy bills, but an estimated 15,000 are still unable to apply.
This is because they do not pay council tax by direct debit - and there are warnings that some of the poorest homes are having to wait the longest.
Campaign group National Energy Action said it is typically the poorest households that do not pay by direct debit - either because they do not have a bank account or because they manage their finances on an ad hoc basis.
Its chief executive Adam Scorer said: "There are serious concerns that those with the greatest need will be least able to access the money."
The government announced the support in February and said councils were expected to start paying the £150 rebates from April.
But many councils have struggled to administer the payments at short notice, including Harrogate Borough Council which said setting up applications for non-direct debit households has been a "complex" process.
A council spokesperson said: "To date, we have paid more than 34,000 households across the Harrogate district the £150 energy rebate.
"The process for launching an application form for non-direct debit payers is complex and also involves pre-payment checks to prevent fraud, as well as a system to ensure payment can be made to eligible residents promptly after making a successful application.
“We anticipate this form being published via our website at the end of the month.”
The payments are being available to homes in council tax bands A to D, and those which pay by direct debit will receive the money automatically.
The different processes for households depending on how they pay council tax has attracted criticism from the local Liberal Democrats which said some residents are being "disadvantaged."
"The application form should have been on the council website immediately.
"In fact, the best way to have done all this would have been to just take the £150 off the council tax bills for this year.
"When I raised this issue at council I was told it was too late as the bills had already been printed, but they could have put an application form in the council tax bill envelope.
"Why insist on people jumping through unnecessary hoops?"
As well as the £150 council tax rebate, the government has also announced a £200 discount on energy bills for all domestic electricity customers from October.
However, unlike the council tax rebate, this discount will be automatically recovered from people's bills in equal £40 instalments over a five year period from 2023, when it is hoped global wholesale gas prices will have come down.
For more information on the council tax rebate go to www.harrogate.gov.uk/council-tax
By Jacob Webster, Local Democracy Reporter