The San Francisco-based bank will still offer its clients a full suite of electronic trading tools to help them execute orders, but will stop offering access to the company's dark pool on Friday, a spokeswoman from the bank told Reuters.

"Our products are customized to fit client trading objectives and the products we offer are aligned with client demand. Effective October 17, our product suite no longer includes the Wells Fargo Liquidity Crosser," the bank said in a statement.

Dark pools are electronic broker-run electronic trading venues, and every big bank has one. They allow investors to trade shares anonymously and only make trading data available after a trade happens, reducing the chance that others in the market will catch wind of the buyer's or seller's intentions and move the price against them.

The move by Wells Fargo comes as regulatory scrutiny over dark pools has intensified over concerns about the lack of transparency in the trading venues. Several regulators have ongoing probes into dark pool operators and New York's attorney general has launched a lawsuit accusing Barclays PLC of securities fraud for activities related to its dark pool.

Wells Fargo said the closure of its dark pool was not due to increased regulatory scrutiny, but rather a lack of demand.

Wells Fargo's dark pool ranks 32nd out of 41 alternative trading systems tracked by the Financial Industry Regulatory Authority in terms of volume. For the week of Sept. 22, the Wells pool traded just under 7 million shares. By comparison, Credit Suisse's dark pool, at the top of the list, traded just under 350 million shares.

With over 40 dark pools competing for much of the same order flow along with 11 U.S. stock exchanges, critics say the venues add to the fragmentation of the market, which increases complexity and costs for market participants.

Wells Fargo said it would still be routing orders to other dark pools for any customer that wishes it to do so.