News that Mercedes conducted a 1000kms test for Pirelli at Barcelona after the Spanish GP has inflamed passions in the paddock and infuriated rival teams.

The heart of the matter is that Pirelli has a contract with the FIA which apparently allows it to call on a team to test during the season when it has some urgent work to do, primarily if there is a safety issue.

Pirelli told the teams about this last year and according to motor sport boss Paul Hembery some agreed to help, and others didn’t reply.

In the aftermath of the controversial Spanish GP, and with changes planned for Montreal, Pirelli asked Mercedes to test, with Lewis Hamilton and Nico Rosberg doing the driving. Due to rain their work extended over three days before the 1000kms was completed.

Incredibly a week passed after the end of the test before the other teams began to learn on Friday in Monaco that it had taken place.

Teams also learned that for at least part of the time tyres that will or could be used in Montreal were under test. And while Pirelli says that the work was aimed at the future that doesn’t seem to gel with the fact that an ‘emergency’ test like this would by definition involve tyres to be used this season – and Pirelli previously made it clear that little or no work is yet going on regarding 2014.

The key issues for angry rivals are a) the FIA’s own sporting regulations confirm that no testing can be done with a current or last year’s car and b) the lack of transparency in what went on.

This blog grabbed Hembery for an exclusive chat. This what he said:

Q: Can you clarify what the situation is?

“We have an agreement with the FIA that states we can do 1000kms tyre testing. It’s something that we had back in the World Rally Championship as well. Last year we wrote to the teams saying this and inviting teams to say yes or no, whether they were willing to do it. Some teams said yes, and some didn’t reply.”

Q: Why was Mercedes involved in the testing?

“Because they were one of the teams that said they would do it. It’s really that. We were in discussions to do some other testing with another team in the future.”

Q: Who was that?

“It’s our business really.”

Q: Why were the other teams not informed it was going on?

“The issue you’ve got is it’s our testing, it’s our work, and what you see is the more discussion you have, the less you manage to achieve. If you start talking about it you end up six months later actually doing it.”

Q: To allow a team to test with a current car and not tell the others was bound to cause some resentment.

“That was not our situation. We asked for a representative car.”

Q: Under the filming days agreement for example other teams are invited to come and observe and so on, and they tell each other what they are doing. You must have realised that when this would came out they would be upset.

“No, because it’s completely irrelevant, it’s not relevant to what’s happening here, what’s going to happen this season. It’s looking at all sorts of solutions that may have relevance in the next 10 years, I don’t know.”

Q: But it did involve the Canadian GP tyres?

“It involved all sorts of tyres.”

Q: But it did involve tyre that you might be running in Canada?

“It involved all sorts of tyres… Let’s turn it round the other way. What do you expect us to do? The rules are very clear, it’s existed in the FIA contracts for years, and we just used it. We’ve got nothing else to add.”

Q: The fact that you did it with a team that’s made very public its issues with tyres, even if a lot of the running wasn’t with tyres that will be used this year, it’s still them running with this year’s car, with Pirelli, getting data. As Christian Horner said it hasn’t hurt Mercedes, has it?

“They [rivals] have no idea what they tested.”

Q: Won’t the fact that you didn’t tell people and even the team’s own dedicate Pirelli engineers didn’t tell them ‘we were in Barcelona last week with Mercedes’ lead to trust issues?

“We go into laboratories, we do a lot of work. We’re doing our job. They don’t tell us what they’re doing. Every team will have the same opportunity at the same time when we introduce something, and that’s it.”

Q: Did you ask anyone else to do that test, or was it just Mercedes?

“We invited all the teams to do 1000kms testing, some replied, some didn’t.”

Q: But that was last year?

“Some replied, some didn’t…”

Q: But for this specific test…

“We don’t need to. Some replied and some didn’t…”