The Consumer Financial Protection Bureau said Thursday private student lenders are making it too tough for borrowers to refinance education loans at lower interest rates and to remove cosigners.

The agency said it has received numerous complaints from borrowers seeking to refinance that lenders are creating potentially illegal difficulties in getting accurate records of their payoffs of the loans so they can apply for cheaper financing and making processing errors.

To ease the path to refinancing, the CFPB said private student lenders should make the payoff records available online and take other steps to quicken the refinancing process.

The agency said student lenders reject 90 percent of applications to remove cosigners (usually parents or grandparents). Those rejections can make it more difficult and costly for the cosigners to refinance their own mortgages.

In another warning on private student loans, the CFPB said most contracts include clauses that have been interpreted to lead to a default, in some cases even if the loan is in good standing, such as “auto-default” clauses where private student lenders and servicers place a loan into default when a borrower’s cosigner dies or files for bankruptcy.

“Private student loan companies should own up to borrowers when they qualify for valuable benefits, clean up contracts with surprises buried in the fine print, and step up to provide borrowers and their co-signers the service they deserve,” said CFPB Student Loan Ombudsman Rohit Chopra.

Over 90 percent of private student loans were cosigned in 2011, up from 67 percent at the start of the recession. Often having a cosigner is the only way to qualify for a private student loan.

The CFPB said the complaints it receives about private student loans are up 34 percent. However, the regulator did not say if this is because bad practices in the industry were becoming more widespread or if knowledge about the complaint process was reaching more borrowers.