The securities and exchange commission of Brazil, CVM, has suspended the public offer of shares in Grupo Oi for up to 30 days, so dealing a setback to its proposed merger with Portugal Telecom.

CVM made its move – according to Reuters – after Zeinal Bava, Oi’s CEO, breached a mandatory quiet period ahead of the offer by making comment to the press.

Oi said it would clarify the situation with the commission as soon as possible and so clear the way for the share offer, which is a key part of the capital-raising plan for CorpCo (the name of the proposed merged entity).

Oi, the fourth-largest mobile operator in Brazil, believes a merger with Portugal Telecom will give it more muscle to compete with bigger rivals. It would also make CorpCo the leading operator in Portuguese-speaking markets.

But though the proposed merger was given approval by Brazilian competition regulator Cade in January, it hasn’t been plain sailing. Oi minority shareholders have repeatedly expressed concern about a lack of say.

Portugal Telecom, already the largest shareholder in Oi, originally planned in October to undertake a capital increase of between BRL7 billion ($3.1 billion) and BRL8 billion to give financial flexibility to CorpCo

Earlier this week, however, Oi shareholders – despite objections from minority shareholders – approved a capital increase of up to BRL14 billion at a meeting in Rio de Janeiro.