BRASILIA (Reuters) - Brazilian President Michel Temer elevated his infrastructure investment secretary to a ministry-level position on Thursday, granting a degree of legal protection to a trusted confidant implicated in a sweeping corruption investigation.

Wellington Moreira Franco, a close adviser to the president, will also be responsible for communications and ceremonies, the presidential spokesman told journalists. He will retain his infrastructure role at Cabinet level.

The promotion highlighted Temer's confidence in Moreira Franco, who, according to a source, had drafted a resignation letter in December after plea bargain testimony in a major graft probe implicated him in illegal campaign fundraising.

Moreira Franco denied any wrongdoing or intentions to quit. His new position in Temer's Cabinet means any case against him must be tried by the Supreme Court, which has a long backlog of cases.

Temer's spokesman also said the president was appointing lawmaker Antonio Imbassahy as his minister in charge of relations with Congress, replacing Geddel Vieira Lima, who stepped down in November amid allegations of influence peddling.

The appointment of Imbassahy, one of five ministers now from the Brazilian Social Democracy Party, or PSDB, in Temer's Cabinet, reflects the president's growing dependence on the allied party to pass economic reforms aimed at closing a huge budget deficit.

The PSDB has pledged to support the government through 2018, when both they and Temer's own Brazilian Democratic Movement Party, or PMDB, plan to field their own presidential candidates.

Given the tensions in some corners of the two parties, Temer waited to announce Imbassahy's appointment until an ideological ally of his was confirmed as speaker of the lower house of Congress earlier on Thursday.

Temer's spokesman also said the president was recreating a Ministry of Human Rights, reversing his decision last year to shutter the ministry and pass its responsibilities to his justice minister.

Temer appointed as human rights minister Luislinda Valois, another member of the PSDB and the first black woman to serve as a judge in Brazil.

(Reporting by Maria Carolina Marcello and Anthony Boadle; Writing and additional reporting by Brad Haynes; Editing by Chris Reese and Peter Cooney)