Labour has told at least 20 staff in its Newcastle communications centre that their jobs will come to an end after Christmas, the Guardian understands.

Party insiders said the team comprised 75 people, more than half of whom were on fixed-term contracts that coincided with the election period.

More than 20 others, some of whom have been in their jobs for up to five years, were called to a meeting on Friday and told their contracts would come to an end, according to one person present.

The staffer, who wished to remain anonymous, told the Guardian the team had been working long hours, in some cases six days a week, through the election campaign, calling voters and urging them to support Labour.

Outside of election periods the unit carried out other tasks such as clearing the email inboxes of Labour frontbenchers, including Jeremy Corbyn, and contacting members to ensure their subscriptions were up to date.

The staffer said they and their colleagues felt let down. “How can I go into the polling station now and vote Labour? It makes me feel like a fool,” they said.

Labour claimed all the staff involved were on fixed-term contracts that had been due to come to an end after the election, and the meeting had been held to confirm that formally. A spokeswoman said: “We don’t comment on staffing matters.”

Some members of the party’s ruling national executive committee say Labour’s finances have become increasingly stretched as the party has employed scores of grassroots community organisers in addition to existing campaign staff.

There was anxious speculation among Labour staff on Friday that other parts of the organisation would also be slimmed down in the weeks ahead as the party sought to hit annual budget targets.

One veteran Labour insider said the communications centre staff were among the lowest paid in the party. “No end to austerity for them,” he said.

On Friday Labour published its regional manifestos, promising to spread “wealth, power and prosperity” across the UK and “bring our country back together”.