Dozens of Labour candidates have been blocked from accessing the party’s canvassing systems, which help them drum up support from voters, because they were deemed not to be campaigning enough in target seats.

In some cases, candidates who have been campaigning every day in battleground seats they are twinned with – as instructed to by Labour HQ – in parts of the home counties and Essex, have still lost their access to key software as their seats are considered either very safe or simply not winnable.

“People in non-battleground seats who are working really hard to gain attention and secure non-Labour voters and could even potentially win have suddenly lost access to this,” a source said. “Some candidates have even been told to stop doing too much because their campaigns are gaining traction.”

Without the software Organise, campaigners are unable to connect with known Labour supporters and mobilise them to canvass. Contact Creator is another key canvassing tool that enables candidates to see people’s individual voting records, and learn if they need to reconnect with larger households who may be split in terms of party affiliation, essentially making it impossible for targeted campaigners to canvass properly.

Meanwhile, Ellie Reeves, the party’s deputy national campaign coordinator, sent an email to candidates, saying: “Anyone who is making more than 500 contacts a week in their own seats will be required to attend five twinned seat campaigning sessions a week.”

Candidates who have been MPs before, or have worked hard within Labour’s grassroots for years, are said to be furious, with some saying they feel “pretty traumatised”. A source said: “It’s a huge mistake to piss off and mobilise senior backbenchers when you will be entirely dependent on totally inexperienced newbies. Most people are telling HQ to fuck off.”

Some candidates have even been banned from printing leaflets in the constituencies they are fighting for, which in some cases have been shown as a neck-and-neck fight in recent polls, and instead ordered to go to a twinned target seat.

Election candidates and activists are concerned at the level of “control” from HQ, and fear it is another example of the party possibly taking Labour voters who are still not sure how to cast their vote for granted.

“It’s unrealistic to expect people to suddenly travel,” said one. “This is meant to be our change election, fighting the far right, fighting for our loyal supporters and winning back those who couldn’t vote for us.”

The Guardian has been told that, on 4 July, seats that Labour currently holds will have no support from the party’s Get Out the Vote, a strategy used to increase voter turnout from loyal supporters. One source called the strategy “just unrealistic” and said that “even under Blair we would be allowed to campaign in our own seats even if they were safe, and then go to marginals later in the day”.

Another said: “They are treating us like children, and particularly the old guard are very pissed off. They want to dictate our every move and are verging on intimidation – it just kills enthusiasm and spirit.”

This strategy “makes sense to people who do things by spreadsheets”, they added. “But this is how we lost Scotland in the past. Luckily for us right now the SNP is falling apart. It seems like HQ are looking at this election as a one-time election win. It’s also bad for many candidates who have been installed and haven’t had to fight for their candidacies. They will be mistaken to believe they will be able to swan around parliament after July 4 without spending time in their constituencies.”

One source said much of the campaign targeting was done on the assumption that polls would narrow and they have not. Some candidates have been concerned about the strategy since as early as Easter, when frontbenchers were told they had a duty to go out canvassing in target seats three times during the recess period and were told to “email the dates” they were doing the visits.

The Labour party declined to comment.