News International's chief executive has expressed frustration with Scotland Yard after another Sun journalist was arrested by officers investigating alleged corrupt payments to officials.

In a strongly worded email to staff on Tuesday, chief executive Tom Mockridge complained that the Metropolitan police ignored pleas from the company to ensure staff detained were treated in a dignified manner.

The journalist, a 37-year-old male, was arrested on Tuesday morning. A 29-year-old male serving Sussex police officer was also arrested by detectives from Operation Elveden. They were taken to separate police stations and later bailed.

Tuesday's was the 14th arrest of a current or former Sun journalist by detectives working on the Met's investigation into alleged illegal payments to public officials. A further three Sun journalists have been arrested in relation to Operation Tuleta, the investigation into alleged criminal breaches of privacy that fall outside Operation Weeting, the phone-hacking probe.

A number have been arrested at their homes early in the morning; some in front of their families. Aggrieved staffers have pointed out that more senior figures connected to News International have been allowed to present themselves at police stations during Operation Elveden and Operation Weeting.

In his email, Mockridge said: "I'm sorry to have to tell you there has been another arrest of a Sun journalist in connection with Operation Elveden.

"The arrest took place earlier this morning. We have given our colleague from the Sun the same legal and practical support that we have offered others.

"We are of course all concerned that these arrests continue to take place. I am also disappointed that representations made on behalf of the MSC [News Corporation's management and standards committee] about how arrests take place have not been taken up.

"We fully accept that the [Met] is within its rights to carry out its duties. However, we had hoped that the high degree of co-operation provided by the company would be reflected in how they conduct their activities. Thank you for all your ongoing hard work."

One source said Mockridge's strongly worded email merely reflected continuing concern at the Sun that even those unaffected by the allegations were being forced to do their jobs in intolerable conditions. "There is absolutely no need for the Met to do it like this," one source said. "The mood here is very low; very grim."

A spokeswoman for News International would not say whether the company will be making further representations.

A spokesman for the Met said the force would not discuss operational matters.

News International journalists have been angry at the Met's treatment of their colleagues since the Operation Elveden arrests began in late January – and at the actions of News Corp's management and standards committee, which was set up last year to phone hacking and other alleged illegal activity by the company's staff.

The Met has made the arrests based on information provided by the MSC. Scotland Yard has stressed that it is not looking for journalists to reveal confidential sources in relation to information obtained legitimately.

Trevor Kavanagh, the Sun's associate editor, wrote a comment piece in February saying there was "a feeling of being under siege" at the paper following the first group of arrests. "The witch-hunt has put us behind ex-Soviet states on free press," he said.

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