Washington ? The Obama administration’s stepped-up demand for tougher restrictions and new taxes on big banks is complicating Senate efforts to write a bipartisan financial regulation overhaul, even drawing a sharp rebuke from a top presidential ally in the Senate.

In an unusual reprimand, Senate Banking Committee Chairman Christopher Dodd, D-Conn., chided administration representatives at the end of a hearing Tuesday for injecting ideas late in his negotiations for a sweeping bill.

Dodd complained that the timing of Obama’s proposal “seemed to many to be transparently political.”

“It’s added to the problems of trying to get a bill done,” Dodd said.

At issue is a proposal that would prohibit large institutions that conduct commercial banking from engaging in speculative trading. The idea had not been included in the administration’s original regulatory plan last June.